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Nature and Art, Vol. VIII, No 1, June 1900

<h3>A PATTERN FLOWER.</h3> JOHN M. COULTER. FLOWERS are of very many patterns, and it must not be supposed that there is any special pattern for them all. There are four parts which belong to flowers in general, and they are repeated in various flowers in numberless ways, or one or more of the parts may be omitted. The flower of the common wild lily, chosen for our illustration, is highly organized, with all the parts represented and well developed. Each part is constructed for some definite work, which we may or may not fully understand. The flower of the illustration shows on the outside six leaf-like bodies, colored a deep orange or reddish, and bearing dark spots. These six bodies are in two sets of three—an outer and an inner set. When there are two sets of these leaf-like bodies the outer set is called the calyx, and the inner one the corolla. The three leaves of the calyx are called sepals, and the three leaves of the corolla petals. In this case the sepals and petals look alike, and then it is usual to speak of the whole set of six as the perianth. In many flowers, however, the sepals and petals do not look at all alike. In the common wake-robin, or Trillium, a near relative of the lily, the three sepals are like ordinary small green leaves, while the petals are much larger and showy, giving the characteristic color to the flower. In the lily it should be further noticed that the sepals and petals are all separate, but in many flowers they are united in various ways to form urns, tubes, funnels, trumpets, etc. The common morning glory is an illustration of a flower in which the petals are united so as to form a beautiful trumpet-shaped or funnel-form corolla. The general purpose of the perianth, that is, the two outer parts of the flower, is to protect the far more important inner parts in the bud, and when the flower opens the perianth unfolds and exposes the inner parts, which are then ready for their peculiar work. The bright color usually shown by the corolla, and sometimes also by the calyx, as in the lily, is probably associated with the visits of insects, which come to the flower for nectar or other food. Since it has been found, however, that some visiting insects are color blind, it is doubtful whether the color is so universal an attraction as it was once thought to be, but it is certainly associated with some sort of important work. A summary of these various duties is as follows: The green, leaf-like calyx is certainly for bud protection; the brightly colored corolla (and sometimes calyx) adds to the duty of protection that of attracting necessary insects, or some other duty that we do not as yet understand. Just within the corolla the third part or set appears, consisting of six stamens. These six stamens are also in two sets of three each, an outer and an inner one. Each stamen consists of a long stalk-like part, called the filament, and at the summit of the filament is borne the anther, which in the lily consists of two long, narrow pouches lying side by side. When the anther is ripe these pouches are filled with a yellow, powdery dust called the pollen. Each particle of this dust-like pollen consists of a minute, but beautifully organized globular body, known as the pollen-grain. The anther pouches are therefore full of pollen-grains. <div class="figcenter"> <ANTIMG src="images/i_008.jpg" alt="" /> <div class="caption">RED OR WOOD LILY. (Lilium Philadelphicum)</div> </div> In the lily it will be noticed that when the anthers are ripe and the pollen is ready to be shed, a slit opens lengthwise in each of the two pouches or sacs. This is the common method for opening the anther sacs, but in some flowers it is curiously modified. For example, in the [Pg 5] heaths, such as the huckleberry, the sacs open by a hole at one end, and sometimes the tips of the sacs are drawn out into long, hollow tubes through which the pollen is discharged. In other cases, as in the sassafras, the sacs open by little trap doors, which swing open as if upon hinges. Of the two parts of the stamen, the filament and anther, the latter is the essential one, so that in some cases the filament may be lacking entirely, only the anther appearing to represent the stamen. Furthermore, the essential thing about the anther is the pollen, to manufacture which is the sole purpose of the stamen. The pollen is necessary to enable the flower to produce seeds, but it must be transferred from the anther which produces it to the fourth part of the flower, not yet described, in which the seeds are formed. This transfer of pollen is known as pollination, and the transfer is usually effected in one of two ways, by the wind or by insects. As a rule, also, the pollen made by one flower must be transferred to some other flower to do its work, and sometimes the other flower may be at a considerable distance. If the pollen is to be transferred by the wind it must be very light and dry, and it must also be very abundant, for the wind is a chance carrier and drops the pollen everywhere in a very wasteful fashion. In such a case the pollen must come down like rain to be sure that some of it strikes the right spot in the right flowers. Occasionally one hears in the papers of "showers of sulphur," which always prove to be showers of pollen carried by the wind from some forest (chiefly evergreen forests) and dropped at random. In the case of pines the minute pollen grains develop wings to assist in the wind transportation. If the pollen is to be transferred by insects it does not need to be so dry and powdery, or so abundant as in the other case, for the insect passes directly from one flower to another, without any random scattering of the pollen. Only winged insects are used for this purpose, as those which must creep, or rather walk, would brush the pollen from their bodies by rubbing against the various obstructions in the way. The insects most commonly used are the numerous kinds of bees, wasps, butterflies, and moths. These insects visit the flowers for different purposes. The butterflies and moths are after the nectar, while the bees and wasps feed upon the pollen. Visiting insects are therefore often grouped as nectar feeders, and pollen feeders, but in either case they are instrumental in transferring the pollen. The fourth or innermost part of the lily flower is an organ called the pistil. It stands in the center of the flower and is composed of three distinct regions. At the base it is bulbous and hollow, containing the bodies which are to become seeds. This bulbous region is called the ovary, and the little bodies it contains, which, through the action of the pollen, are to become seeds, are called ovules. Rising from the top of the ovary is a slender, stalk-like part called the style; and at the top of the style is a knob-like region called the stigma. The most essential region of the pistil is the ovary, for it contains the ovules. Next in importance is the stigma, for it must receive the pollen-grains. The style is of least importance, and therefore is sometimes wanting, the stigma being directly upon the ovary. The duty of the style, when it is present, seems to be to put the stigma into a favorable position to receive the pollen. It must not be supposed that the stigma always resembles a knob-like top to the style. It is really only a surface prepared to receive pollen, so it may be upon the top of the style, or may run like a line down one side of it, or may display itself in some other way. The pistil of the lily, however, is not a single structure. If the ovary be cut across, it will be found to be made up of three compartments, each one of which contains ovules. Each one of these compartments represents a unit of structure which has entered into the formation of the pistil. These units are called carpels, and the pistil of the lily is made up of three carpels. In this case the three are distinct only in the ovary, and have completely lost their identity in the region of the style. In many relatives of the lily, however, the three carpels are kept distinct in the style region, three styles or a three-parted style appearing upon the ovary. In some flowers the carpels are kept [Pg 6] entirely distinct, each one having its own ovary, style, and stigma. For example, in the buttercup there is a little mound in the center of the flower made up of numerous pistils, each consisting of a single carpel. It is evident, therefore, that a pistil may consist of one carpel or several carpels, and that in the latter case the carpels may be more or less completely united. The sure indication of a carpel is that each carpel bears its own ovules. In some flowers there is but a single carpel, as in peas and beans, whose pods have developed from a pistil consisting of a single carpel, as is indicated by the single lengthwise set of seeds. In some plants the flowers do not have all the four parts described above. In some cases the petals may be lacking, the one set of perianth parts represented being regarded as the calyx, although it may look like a corolla, as in the clematis or anemone. Such flowers are said to be apetalous, which means "without petals." In other cases both the calyx and corolla may be wanting, the flower consisting of only stamens and carpels. Such flowers are spoken of as naked. In other flowers the stamens may be lacking, and as the pistil is the only essential part present such flowers are said to be pistillate. It may be counted upon, however, that if there are pistillate flowers there are also corresponding staminate flowers in which the pistils are lacking and the stamens present. In such cases both staminate and pistillate flowers may occur on the same plant, or they may occur on different plants, so that there may be not only staminate and pistillate flowers, but also staminate and pistillate plants. It also sometimes happens that staminate and pistillate flowers are also naked, so that in such cases the flower is represented by stamens alone, or even by a single stamen, or by carpels alone, or by a single carpel. It would be hard to imagine a more simple flower than one composed of a single stamen or a single carpel. Such flowers may be found in the willows. In this study of the lily it should be observed that the number three runs through all the parts of the flower. The flower formula may be expressed as follows: sepals 3, petals 3, stamens 3 plus 3, carpels 3. This number is established in many families related to the lilies, and is one of their characteristic features. In other groups of flowering plants a different number is established, the number five being the most common. For example, in the common wild geranium the flower formula is as follows: sepals 5, petals 5, stamens 5 plus 5, carpels 5. In still other flowers the number four is established. In many common flowers it will be noticed that no definite number is established, or that it is not completely established. For example, in the common wild rose there are 5 sepals and 5 petals, but an indefinite number of stamens and carpels; while in the water lily there is no definite number established, the sepals being usually 4, and the other parts indefinitely repeated. In those flowers in which some number is definitely established, it often happens that one set may be reduced in number, and this is usually the carpel set. In the families of highest rank among flowering plants, such as the figworts, mints, and composites (sunflowers, asters, dandelions, etc.) the flower formula is sepals 5, petals 5, stamens 5, and carpels 2. Another fact shown by the lily flower is that the different sets alternate with each other in position. The three petals do not stand directly in front of the three sepals, but in front of the spaces between the sepals. In the same way the three outer stamens alternate with the petals; the inner stamens alternate with the outer ones; and the three carpels alternate with the inner set of stamens. It is very uncommon to find one set standing directly in front of the next outer set, and this position opposite the other set always needs some special explanation. As a rule, therefore, the flower sets alternate with one another, but in some cases a set may be opposite. The history of a flower does not end with the opening of the blossom. If the stigma has succeeded in receiving some pollen, and the pollen has succeeded in doing its work, the ovules within the ovary become gradually transformed into seeds, and the ovary becomes transformed into the fruit, the outer sets of the flower usually disappearing. In the lily [Pg 7] these fruits take the form of dry pods, some of which may be seen in the illustration. Such pods have various ways of opening to discharge their ripened seeds. In many cases the commonly recognized fruit includes more than the ovary. For example, in the apple and pear the modified ovary is represented by what is called the "core," and the pulpy part outside, forming the edible part of the fruit, is the thickened calyx. In the strawberry the real fruits are the small, nut-like "pits" which are more or less imbedded in the surface, while the pulpy part is the very much enlarged and fleshy tip of the stem which bore the numerous carpels. In the pineapple the change involves a whole flower cluster, and a pineapple is a cluster of flowers which has formed a pulpy mass, flowers, leaves, stems, and all. From what has been said it will be noticed that some fruits ripen dry, as in the case of the lily pod, bean pod, etc., and that others ripen fleshy, as in the case of apples, strawberries, etc. It must not be supposed that flesh can only be formed by parts outside of the ovary, for the peach is a modified ovary, whose wall has separated into two layers, the outer of which forms the pulp, and the inner the "stone," the kernel within the stone being the real seed. Whatever form or structure the fruit may take, everything is with reference to the dispersal of the seeds, which must be carried to places suitable for their germination. How seeds are carried about is a long story, which must be deferred to some later time, but it belongs to the general subject of flowers. It will be seen from the above brief account that flowers occur in almost infinite variety, so that we are able to tell the various groups of flowering plants by the kind of flowers they produce. Amidst all of this infinite variety, however, there are but two purposes shown, the variety being merely the different ways in which different plants have carried them out. These two purposes are the securing of pollination, in order that seeds may be formed, and the proper distribution of the seeds. All structures found in flowers should be made to answer these two problems. <hr> <div style="break-after:column;"></div>

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