Chapter VII: The Flower (2)

=260. Fixing the type.=—It is the tendency of plants to vary under the influence of climate, soil, food supply, crossing, and other causes perhaps unknown to us, that makes the plant breeder’s art possible. When a horticulturist sets out to produce a new fruit or vegetable, he first forms in his mind a clear idea of what he wants—whether increase of yield or size, resistance to cold, drought, or disease, improvement in flavor, color, shape, etc., or change in the time of maturing or flowering (early and late varieties). Suppose, for instance, he wishes to produce an oxeye daisy with all the disk florets changed to white ones like the rays. He will begin by selecting plants with the greatest number of rays and the most conspicuous ones that he can find, and sowing the seeds of the flowers which show the greatest tendency to the development of these qualities. He will continue this process from generation to generation, rigorously destroying all specimens that do not approach nearer the ideal sought, until all disposition to “rogue,” as the tendency to revert is called, has been eliminated. When variations cease to occur and the seed of the new variety always “come true,” the type is said to be _fixed_; though some care will always be necessary to keep it so, as the influence of changed surroundings and the danger of mixture with foreign pollen must always be provided against.

=261. Survival of the fittest.=—In the fierce struggle continually going on among both plants and animals for food, shelter, and elbow room in the world, any individual that happens to vary in a way which adapts it to its surroundings a little better than its rivals, has an advantage that will enable it to survive when less favored members of the species will perish. Its offspring, or some of them, may inherit this quality and transmit it, with the attendant advantage, to their posterity, and so on, till that particular breed outstrips all competitors, and in time, as the less favored intervening forms die out, becomes differentiated as a new species. This is, in brief, the doctrine of natural selection and the survival of the fittest.

=262. Artificial selection.=—Artificial selection enables the breeder to accomplish more quickly what nature appears to do by the slow process of natural selection. It is by this means that our choicest fruits and vegetables have been developed from greatly inferior, and sometimes inedible, wild forms. Plants respond so readily to the influence of selection, and the changes brought about by it are so rapid, that new styles of fruits and flowers succeed each other in the market with almost as great frequency and in as ready response to demand as the new styles of women’s bonnets and gowns in the shop windows.

=263. Causes of variation.=—While man cannot directly force plants to vary in any given direction, he can hasten the process of variation by crossing, or by changing the conditions under which they are growing. This is called “breaking the type.” Hybridization furnishes the readiest means to this end. Change of food supply, especially if accompanied by excess of nourishment, is probably the expedient that ranks next in effectiveness. Light, temperature, moisture, character of the soil, exposure to wind, and the like, also have their influence; and in adapting themselves to changes in these various conditions, plants are apt to exhibit an unusual number of variations, when removed from one locality to another, especially if the difference in soil and climate is very marked. Now comes the breeder’s opportunity. By taking advantage of such variations as may occur either spontaneously, or as the result of his efforts to break the type, he will generally find some that will meet his requirements; and knowing the effect produced by different conditions, he can, to a certain extent, influence the course of variation in the direction desired, by subjecting his specimens to the conditions that tend to produce it. If he wishes to develop a dwarf variety, for instance, he will take notice that overcrowding, lack of nourishment, and cold tend to produce that result in nature, and by acting on this hint he can direct his efforts more intelligently. He will learn, too, not to waste time in trying to breed a plant contrary to its nature. He must not expect to gather figs from thistles by any art of selection or skill in culture. By attention to Mendel’s law, a still further saving of time and labor may be effected.

It is obvious, from what has been said, that a breeder’s chance of finding what he wants will be greater in proportion to the number of individual plants he has to choose from. For this reason, a horticulturist sometimes uses thousands and hundreds of thousands of specimens of a single kind in conducting his experiments. In this way he compresses into a short space of time the advantage that nature can gain only by spreading her random experiments over a long series of years, or even centuries.

=264. Mutation and variation.=—There are at least two ways in which changes in vegetable and animal forms are thought to occur: (1) by the preservation and fixation through selection and heredity, of slight differences that may appear from time to time, such divergences being called “fluctuating variations”; (2) by the appearance now and then, due to causes as yet unknown, of definite and sudden changes creating a new form at a single, though perhaps small, leap. When such a change is temporary and passes away with the individual in which it first appeared, it is called a “sport,” and leads to no important results; but when it is inherited by the offspring, so that it is capable of giving rise to a new species, it constitutes a “mutation.” The value of a mutation to breeders in saving time and trouble is obvious. Professor Hugo de Vries, a Dutch botanist, was the first to call attention to the importance of mutation and its bearing upon the production of new species.

=265. Factors in the evolution of species.=—Variation, heredity, and selection are the three principal agents underlying all changes, whether for the improvement or deterioration of living organisms. The influence of external surroundings in keeping up a variation once begun, or in starting new ones, is also a factor that cannot be disregarded. It is for this reason that natural species are so much more stable than those brought about by man. The former, being evolved in response to natural conditions, are liable to change only as alterations in their surroundings are brought about by the slow operation of natural causes. But the types resulting from the breeder’s art, produced as they often are in response to human demands and in direct opposition to the requirements of natural conditions, are in a sense purely artificial, and can be preserved only by keeping up the artificial surroundings by which they were developed. Hence, the importance of diligent cultivation and constant care and tillage, without which the most carefully selected stocks may quickly “run out” and degenerate into worthless forms.

Practical Questions

1. Which are the more pliable to the breeder’s art, annuals or
perennials? Why? (91, 93, 262, 263.)

2. What advantage is gained by using buds and grafts instead of
seedlings in making new varieties of fruit trees? (257, 259, 260.)

3. Would it be practicable to breed new varieties of slow-growing
forest trees, like oak, cypress, redwood, from seeds? Why or why
not? (93, 262, 263.)

4. Can you account for the existence of the numerous intermediate
forms between the different species of oaks found in nature? (255,
257.)

5. If a breeder wished to produce a sweet-scented daisy or pansy,
how would he make his selections? (260.)

6. Which would be the more useful for his purpose, a plant that
showed a general tendency to variability, or one that remained
steadily fixed to its type? (260.)

7. What could he do to break the type? (263.)

8. Would an intelligent breeder set out to produce edible roots and
tubers from wheat or barley? (263.)

9. Would he think it worth while to try to develop a fleshy fruit
from a filbert or a walnut tree? From a haw? From sheepberry and
black haw? From tupelo (ogeechee lime)? (263.)

10. Suppose a florist should wish to change the color of a rose
from pink to deep red; how could he hasten the process? (257, 263.)

11. Explain why it is so much easier to produce new varieties of
plants when there are already many kinds in existence, as, for
example, the rose, peach, and chrysanthemum. (255, 256; Exps. 78,
79.)

VIII. ECOLOGY OF THE FLOWER

A. THE PREVENTION OF SELF-POLLINATION

MATERIAL.—Any kind of unisexual flowers obtainable. Some good
examples for illustrating points mentioned in the text are: for
spring and early summer, catkins of almost any of our common forest
trees,—oak, hickory, willow, poplar, etc.; tassels and young ears
of early corn; for summer and early fall, flowers of late corn, and
of melon, squash, pumpkin, or others of the gourd family. Examples
of _dichogamy_ are: evening primrose, showy primrose (_Œnothera
speciosa_), willow herb (_Epilobium_), dandelion, artichoke,
sunflower, or any of the composite family; of _dimorphism_:
English primrose (_Primula_), loosestrife (_Pulmonaria_), bluets
(_Houstonia_), partridge berry; _cleistogamic_: fringed polygala,
violets. Peanuts, while not technically classed as cleistogamic,
are strictly close-fertilized, and approach the type so nearly that
they may be used as an illustration.

=266. Ecology= is the study of plants and animals in relation to their surroundings. The principal modifications that flowers undergo in this respect are in adapting themselves for (1) pollination, and (2) protection.

=267. Unisexual flowers.=—The advantages of cross fertilization were shown in the last two sections. It was also shown that the first step taken by the breeder to secure this result is to render the flower incapable of self-fertilization, by removing the stamens. Nature accomplishes the same purpose by the more effectual expedient of providing imperfect, or _unisexual_ flowers, in which stamens only, or pistils only, occur in the same flower. When the stamens alone are present, the flower is said to be staminate, or _sterile_, because it is incapable of producing seeds of its own, though its pollen is a necessary factor in seed production. If, on the other hand, the ovary is present and the stamens absent, the flower is pistillate and _fertile_; that is, capable of producing fruit when impregnated with pollen. Sometimes both stamens and pistils are wanting, as in the showy corollas of the garden “snowball,” the hydrangea, and the rays of the sunflower. Such blossoms are said to be _neutral_, from the Latin word _neuter_, meaning neither, because they have neither pistils nor stamens. They can, of course, have no direct part in the production of fruit, but are for show merely. (231.)

=268. Monœcious and diœcious plants.=—When both kinds of flowers, staminate and pistillate, are borne on the same plant, as in the oak, pine, hickory, and most of our common forest trees, they are said to be _monœcious_, a word which means “belonging to one household”; when borne on separate plants, as in the willow, sassafras, and black gum, they are _diœcious_, or “of two households.” Draw a flowering twig of oak, pine, or willow. Where are the fertile flowers situated? Notice how very much more numerous the staminate flowers are than the fertile ones. Why is this necessary? (275.)

=269. Dichogamy= is the name applied to a condition where the stamens and pistils mature at different times, as in the evening primrose, oxeye daisy, and most of the composite family. It is a very common method in nature for preventing self-pollination, and quite as effective as the monœcious arrangement, since it renders the flowers practically unisexual.

=270. Dimorphism= denotes a condition in which the stamens and pistils are of different relative lengths in different flowers of the same species, the stamens being long and the pistils short in some, the pistils long and the stamens short in others. Flowers of this sort are said to be _dimorphous_, or _dimorphic_, that is, of two forms; and some species are even _trimorphic_, having the two sets of organs long, short, and medium, respectively, in different individuals. Examples of dimorphic flowers are the pretty little bluets (_Houstonia cœrulea_), the partridge berry, the swamp loosestrife, and the English cowslip. Of trimorphic flowers we have examples in the wood sorrel and the spiked loosestrife (_Lythrum salicaria_) of the gardens. These flowers were a great puzzle to botanists until the celebrated naturalist, Charles Darwin, proved by experiment that the seeds produced by pollinating a dimorphous flower with its own pollen, or with pollen from a flower of similar form, are of very inferior quality to those produced by impregnating a long-styled flower with pollen from a short-styled one, and _vice versa_.

=271. “Nature abhors self-fertilization.”=—These are the three principal methods by which nature provides against self-fertilization. Other cases occur in which the relative position of the two organs is such that self-pollination is difficult, or impossible, as in the iris and bear’s grass; or the pollen may be incapable of acting on the stigma of the flower that produced it. This aversion to self-fertilization is so great that many flowers, even when capable of it, will give preference to the pollen of another plant of the same kind, if dusted with both. From his observations on the behavior of plants in reference to this function, Charles Darwin drew the conclusion that “Nature abhors perpetual self-fertilization.”

=272. Cleistogamic flowers.=—Apparent exceptions to this rule are the hidden flowers found on certain plants which seem to have been constructed with a special view to self-fertilization. They are called _cleistogamic_, or closed, because they never open, but are fertilized in the bud; and those of the fringed polygala do not even rise above ground at all. Flowers of this kind can be found on several species of violet, concealed under the leaves, close to the ground; and the flowers of the peanut, found in the same situation, while they open slightly, are close-fertilized and practically cleistogamic. They are much more prolific than ordinary flowers, but are not common, and seem to be a provision against accident, for the plants producing them are generally provided with other flowers of the usual kind,—some, as the violet, having elaborate special adaptations for cross fertilization.

Practical Questions

1. Why does a strawberry bed sometimes fail to fruit well, although
it may flower abundantly? (267, 268.)

2. Are berries found on all sassafras trees? On all buckthorns?
Hollies?

3. Would a solitary hop-vine produce fruit? A solitary ash tree?
(267.)

4. Why is a mistletoe bough with berries on it so much harder to
find than one with foliage merely? (267, 268.)

B. WIND POLLINATION

MATERIAL.—In spring, catkins of forest trees, staminate and
pistillate flowers of pine. At nearly all seasons, heads of grain
and panicles of various kinds of grass can be obtained. For
experiment, a potted plant of any kind, just about to bloom, may be
used.

EXPERIMENT 80. TO TEST THE EFFECT OF SHUTTING OUT EXTERNAL
AGENCIES.—Tie paper bags over flower buds of different kinds when
nearly ready to open and leave until the flowers have withered.
On removing the bags, mark with colored threads the flowers that
had been covered, and watch until seed time. Do you notice any
difference in the number, size, or weight of the seed produced by
them and by those of the same kind left exposed? How do you account
for the difference, if there is any? By what agencies could foreign
pollen have been carried to the stigmas of the exposed flowers? If
any of the covered specimens wither and drop their seed vessels
without any attempt to fruit, examine a fresh flower, and see if it
is capable of self-pollination.

As already explained, experiments of this kind, to be conclusive,
should be tried on as many specimens as possible. The greater the
number of species and individuals included, the better. Where it is
not practicable to carry on experiments by the class, pupils who
are interested can make them at home.

=273. The problem of pollination.=—When a plant has provided against self-pollination, its problem is only half solved, as it must now depend upon the conveyance of pollen to the stigma by extraneous means.

=274. Adaptations to wind pollination.=—A very large number of plants, among which are included nearly all our principal forest trees, grains, and grasses of every kind, depend exclusively upon the wind for the distribution of their pollen. This being the case, it is, of course, an advantage to them to get rid of all unnecessary appendages that might hinder a free play of the wind among their flowers, and so they consist, as a rule, of essential organs only (Figs. 341, 342). Such flowers are often distinguished, however, especially among grasses and low herbs, by large, feathery stigmas that are well adapted to catch and hold any stray pollen grains which may be floating in the air. Place a stigma of oat or other grass under the microscope and you will probably see a number of pollen grains clinging to its branches.

=275. The disadvantages of wind pollination.=—This is a very clumsy and wasteful method, however, for so much pollen is lost by the haphazard mode of distribution that the plant is forced to spend its energies in producing a vast amount more than is actually needed, and great masses of it are frequently seen in spring floating like patches of sulphur on ponds and streams in the neighborhood of pine thickets. Like those that are self-pollinated, wind-pollinated flowers are generally very inconspicuous, devoid of odor, and of all attractions of form or color, because they have no need of these allurements to attract the visits of insects. Besides being wasteful, wind pollination is very uncertain. The pollen cannot be blown about very well unless it is dry, and in rainy weather it may all be rotted or washed away before it can reach the stigmas that are ready to receive it.

Practical Questions

1. Why do the flowers of oak, willow, and other wind-fertilized
plants generally appear before the leaves? (274.)

2. Can you account for the showers of “sulphur” sometimes reported
in the newspapers? (275.)

3. Do you see any connection between the feathery stigmas of most
grasses and their mode of pollination? (274.)

4. Why are house plants not apt to seed so well as those left in
the open? (Exp. 80.)

5. Why are the tassels of corn placed at the tip of the stalk?
(274.)

6. Can you trace any connection between the winds and the corn
crop? (274.)

7. If March winds should cease to blow, would vegetation be
affected in any way? (274.)

8. Why are wind-fertilized plants generally trees or tall herbs?
(274.)

9. Is it good husbandry to plant different varieties of corn or
other grain in the same field, if it is desired to keep the strain
pure? (255, 274.)

10. Is water a good pollen carrier? (275.)

11. What is the only class of plants it is likely to reach?

12. What is the only other agency, besides wind and water, by which
this office can be performed?

C. INSECT POLLINATION

MATERIAL.—Half a dozen panes of glass, about 6 × 9; squares of
bright-colored cloth or paper; a few spoonfuls of honey or sirup;
perfumes of various kinds, preferably flower extracts; fetid and
disagreeable smelling substances, such as a bit of decaying animal
or vegetable matter. Observations on living plants can best be made
out of doors or in a greenhouse, as opportunity offers.

EXPERIMENT 81. HAS THE COLOR OF FLOWERS ANY ATTRACTION FOR
INSECTS?—Place half a dozen panes of ordinary window glass out of
doors or in an open window to which insects can have free access.
Lay under the first pane a piece of black paper or cloth, and under
the others bright-colored pieces of red, blue, white, yellow, and
purple. Drop on the center of each pane a little honey or sirup,
and watch. Do insects show any color preferences? Which color
attracts fewest visitors? Which most?

EXPERIMENT 82. DOES ODOR INFLUENCE INSECTS?—Try the same experiment
with different odors, removing the bright colors and sprinkling
some kind of perfume on each pane. Try also the effect of decaying
meat and other malodorous substances. Are any insects attracted
by these? What kinds? Does this account for the noisome smells
of the “carrion-flower” and skunk cabbage? What kinds of insects
are attracted by sweet-smelling substances? Do the greater number
appear to be attracted by these, or by foul odors? Are flowers of
the sweet-smelling or the foul-smelling kind more common in nature?
Do insects seem to be more strongly influenced by colors or by
odors?

=276. The color of flowers=, being an adaptation to changing external conditions, is a very unstable quality, and varies greatly within the limits of the same species. Even on the same stem, flowers of different colors are often found, due, probably, to hybridization. Yet, notwithstanding all this apparently random intermingling of hues, the range of color for each species is confined, approximately, within certain limits. Nobody has ever seen a blue rose or a yellow aster; and though the florist’s art is constantly narrowing the application of this law, it still remains true that in a state of nature, certain colors seem to be associated together in the floral art gamut. Yellow is considered the simplest and most primitive color in flowers, and blue the latest and most highly evolved. Yellow, white, and purple, in the order named, are the commonest flower colors in nature; blue, the rarest. Do you see any relation between these facts and the color preferences of insects?

=277. Advantages of insect pollination.=—It is evident that this is a much more certain as well as a more economical method of securing pollination than through the haphazard agency of wind or water. In probing around for the nectar or the pollen upon which they feed, these busy little creatures get themselves dusted with the fertilizing powder, which they unconsciously convey from the stamen of one flower to the pistil of another. Insects usually confine themselves, as far as possible, to the same species during their day’s work, and since less pollen is wasted in this way than would be done by the wind, it is clearly to the advantage of a plant to attract such visitors, even at the expense of a little honey, or of a liberal toll out of the pollen they distribute.

=278. Special partnerships.=—Some plants have adapted themselves to the visits of one particular kind of insect so completely that they would die out if that species were to become extinct. The well-known alliance between red clover and the bumblebee was brought to light when the plant was first introduced into Australia. It grew luxuriantly and blossomed profusely, but would never set seed till the bumblebee was introduced to keep it company.

A remarkable partnership of this kind exists between the _pronuba_, or yucca moth, and the flowering yuccas, of which the bear’s grass and Spanish bayonet are familiar examples. The pods of these plants are never perfect, but all show a constriction at or near the middle, such as is sometimes seen in the sides of wormy plums and pears. This is caused by the larvæ of the moth, which feed upon the unripe seeds. A glance under the nodding perianth of a yucca blossom (Fig. 354) will show that the short stamens are curved back from the pistil in such a manner that, under ordinary circumstances, the pollen cannot reach the stigma except by the rarest accident. But the yucca moth, as soon as she has deposited her eggs in the seed vessel, takes care to provide a crop of food for her offspring by gathering a ball of pollen in her antennæ and deliberately plastering it over the stigma (Fig. 353). In this way fertilization of the ovules and maturing of the fruit is secured. The larvæ feed on the unripe seeds for a time, but so few are destroyed in proportion to the number matured that the plant can well afford to pay the small toll charged in return for the service rendered.

=279. Caprification of the fig.=—A more complicated case of specialization is that of the Smyrna fig of commerce—the only one of the species that is capable of perfecting seeds. The staminate flowers are borne on a separate tree, the caprifig, which grows wild in the countries bordering on the Mediterranean. The caprifigs, as the fruit of this tree is called, are worthless except as the breeding and nesting places of a small insect, the fig wasp. This insect is the necessary agent in conveying pollen from the stamens of the caprifig to the pistils of the Smyrna fig, which it penetrates at certain seasons of the year in the effort to lay its eggs. In order to insure _caprification_, as this process is called, the caprifigs are strung by hand on fillets of cord or raffia and hung about on the trees which are to be fertilized. In this case we have an example of a threefold partnership between man, the fig tree, and the wasp, which is necessary to the existence of two of the parties.

D. PROTECTIVE ADAPTATION

EXPERIMENT 83. ARE THE FLORAL ENVELOPES OF ANY USE?—Carefully
remove the calyx and corolla from a young flower bud on a growing
plant and see what will happen. Remove them from a flower just
unfolding. Mark each by tying a colored thread lightly around the
petiole and see if it sets as many seeds, or as good ones, as the
unmutilated flowers on the same plant.

EXPERIMENT 84. IS THE POSITION OF A FLOWER ON THE STEM OF ANY
IMPORTANCE?—Invert a blossom of pea or sage, and see what parts
would come in contact with the body of a visiting insect. How would
its chances for pollination be affected? Try to make a flower grow
in an inverted position by tying or weighting it down, and watch
the effect on seed production.

EXPERIMENT 85. IS THE POSITION OF FLOWERS ON THE STEM INFLUENCED
BY LIGHT?—Place a potted plant with expanding flower buds near a
window so that the light will reach it from one side only, and
notice the position of the buds. After a day or two reverse the
position with regard to light, and watch whether any change of
position takes place.

EXPERIMENT 86. IS THE POSITION OF FLOWERS ON THE STEM INFLUENCED
BY GEOTROPISM?—Lay a potted plant of lily of the valley, larkspur,
gladiolus, or digitalis in a horizontal position, tie the main stem
to keep it from changing its direction of growth, and leave for two
or three days in a place where it is lighted equally on all sides.
How do the individual flowers behave? What part bends to turn them
up? Vary the experiment by turning the pot bottom upwards so
that the flowering axis will point downwards. This can be done by
inclosing the pot in a bag of strong cheesecloth, with the string
tied loosely but firmly around the foot of the stem to prevent the
contents from falling out, and suspending the whole bottom upwards.
In making these experiments, use flowers that grow in a long
cluster, or raceme, and hold the main axis in a vertical position
by tying or weighting it down. Watch the behavior of the individual
flowers. Arrange another pot containing the same kind of plant, in
the same way, and suspend one in a dark place, keeping the other
in the light. Does the same movement take place in both? Is it in
response to light, or to gravity?

=280. Means of protection.=—Where plants have adapted themselves to insect pollination, it is, of course, important to shut out intruders that would not make good carriers. In general, small, creeping things, like ants and plant lice, are not such efficient pollen bearers as winged insects, and hence the various devices, such as hairs, scales, and constrictions, at the throat of the corolla, by means of which their access to the pollen is prohibited. To this class of adaptations belong the hairy filaments of the spiderwort, the sticky ring about the peduncles of the catchfly, the swollen lips of the snapdragon, the scales or hairs in the throat of the hound’s-tongue, the velvet petals of the partridge berry, and the recurved edges of corollas like those of the morning-glory and tobacco, over which small crawling insects cannot easily climb.

Of flowers that are pollinated by night moths, some close during the day, as the four-o’clock and the evening primrose; and _vice versa_, the morning-glory, dandelion, and dayflower (_Commelyna_) unfold their beauties only in the sunlight. For similar reasons, night-blooming flowers are generally white or very light-colored, and shed their fragrance only after sunset. A nodding position is assumed by many flowers at night, or during a shower, to keep the pollen from being injured by dew or rain.

=281. Insect depredators.=—The secretion of honey is a common means of attracting insects, and various adaptations, such as spurs, sacs, and pockets, are provided for protecting it against unwelcome intruders. In general, plants that have long, tubular flowers, like the trumpet honeysuckle (_Lonicera sempervirens_) and the trumpet vine, are reserving their sweets for humming birds, or long-tongued moths and butterflies. This protective device is not always successful, however, against insect depredators, for it is not uncommon to find such corollas with a puncture near the base, made by wasps or bees, and sometimes by humming birds themselves, in their impatience to get at the feast before the flower is open. Through the breach thus made, a rabble of petty thieves can then find entrance.

Practical Questions

1. Of what use is the brilliant coloring of the camellia? The large
flowers of the magnolia? The perfume of the rose and the violet?
The fetid odor of the ailanthus? (277; Exps. 81, 82.)

2. Are the tastes of insects in regard to odors always the same as
ours? (Exp. 82.)

3. Have flowers any economic value except for decorative purposes?

4. Can you name any that are used as food or beverages? Any that
furnish spices and flavorings? Drugs, medicines, or dyes?

5. What commercial food product is obtained almost entirely from
flowers?

6. Name some of the flowers that are most valued by the beekeeper.

7. Mention another important industry that is entirely dependent on
flowers.

8. Name some of the flowers that are most important to the perfumer.

9. Why do the seeds of fruit trees so seldom produce offspring true
to the stock? (256, 257, 271, 277.)

10. Would you place a beehive near a field of buckwheat? Of clover?
Near a strawberry bed? In a peach orchard? Near a fig tree? Under a
grape arbor?

11. Why are very conspicuous flowers, like the camellia, hollyhock,
and pelargoniums, so frequently without odor?

12. Why is the wallflower “sweetest by night”? (280.)

13. What advantage can flowers like the morning-glory gain by their
early closing? (280.)

14. Of what use to the cotton plant, Japan honeysuckle, and
hibiscus is the change of color their blossoms undergo a few hours
after opening? (277, 278, 280.)

15. Why does the Japan honeysuckle, which has run wild so
abundantly in many parts of our country, produce so few berries?
(278, 280.)

16. If the trumpet vine grows in your neighborhood, examine a
number of corollas and account for the dead ants found in them.
Account also for the large hole (sometimes three quarters of an
inch in diameter) often found near the base of the tube. (281.)

17. Do you see any connection between the greater freshness and
beauty of flowers early in the morning, and the activity of bees,
birds, and butterflies at that time?

18. The flowers most frequented by humming birds are the trumpet
honeysuckle, cardinal flower, trumpet vine, horsemint (_Monarda_),
wild columbine, canna, fuchsia, etc.; what inference would you draw
from this as to their color preferences?

Field Work

1. The ecology of the flower is so suggestive a subject and so
peculiarly appropriate to outdoor work that it seems hardly
necessary to point out the many attractive fields of inquiry it
opens to the student of nature. In this way alone can experiments
in insect pollination be carried on to the best advantage. Try
the effect of enveloping buds of various kinds in gauze so as
to exclude the visits of insects, and note the result as to the
production of fruit and seed. Envelop a cluster of milkweed
blossoms in this way and notice how much longer the flowers so
protected continue in bloom than do the others; why is this? Try
the same experiment upon the blooms of cotton and hibiscus, if you
live where they grow, and see whether the characteristic change in
color occurs in flowers from which insects have been excluded, and
whether good seed pods are produced by them. Try the effect upon
fruit production of excluding insects from clusters of apple, pear,
and peach blossoms.

2. Make a list of all the outdoor plants, both wild and cultivated,
that are found blooming in your neighborhood, keeping a record of
the earliest specimens of each as you find them. The best way is to
keep a sort of daily calendar, and at the end of each month give a
summary of the species found in bloom during that period. In this
way a fairly complete annual record of the flowering time of the
different plants for that vicinity will be obtained. The record
should be kept up the whole year round. Don’t stop in winter,
but go straight on through the coldest as well as the hottest
season, and you will make some surprising discoveries, especially
if the record is continued year after year. Give the common name
of each plant, adding the botanical one if you know it. Any facts
that you may know or may discover in regard to particular plants,
such as their medicinal or other uses, their poisonous or edible
properties, the insects that visit them, and in the case of weeds,
their origin and introduction, will greatly enhance the interest
and value of the record.