Page:The New International Encyclopædia 1st ed. v. 07.djvu/848

FLOWER. FLOWER. bloma, Icel. blome, Eng. bloom, lr. blfitli. Bower, and ultimately with Lat. folium, <ik. <pvov, phyllon, leaf). A structure developed by the higher plants only, and chiefly concerned in the production of seeds. An exact definition of a flower is very difficult, but the popular con- ception is clear enough for this presentation. Not all plants which produce seeds can be said to have true flowers, since the conifers and their allies no more possess true flowers than do many of the fern-plants. Parts of Flower. The parts of an ordinary flower may lie illustrated by the buttercup. In this case it is observed that four distinct mem- bers enter into the organization of the flower. The outermost set is a "calyx,' whose individual members are the 'sepals;' the next inner set is the 'corolla.' whose individual members are the 'petals;' the 'stamens' form the third set; and the 'carpels' are in the centre. The sepals and the petals are the characteristic floral leaves, while the stamens and carpels are the spore-pro- ducing members (sporophylls) . The calyx and corolla taken together are frequently spoken of as the 'perianth,' the name being specially applied in case the two are similar, as in the lily. Since the whole purpose of the flower may be said to be the production of seed, the stamens and carpels are the essential organs; without them no seed could be produced. In another sense, however, the calyx and corolla are the characteristic or- gans, since it is their association with the sta- mens and carpels which distinguishes the true flower of the highest group of plants (angio- sperms ) . Functions of Parts. The calyx is usually merely a protective structure, being generally leaf-like or bract-like, and investing the more delicate inner members in the bud. The corolla is usually connected with pollination (q.v. ), be- ing in general the conspicuous and showy part of the flower. The stamens produce the pollen ; while the carpels produce the ovules, which later become the seeds. The stamen usually has two regions, a stalk-like portion called the 'filament,' and a spore-bearing region called the 'anther.' The carpel usually has two regions, the basal part, containing the ovules, being the 'ovary,' and the more or less elongated beak-like process from it being the 'style.' The style always presents in some portion, frequently the tip, a specially pre- pared surface, known as the 'stigma,' for the re- ception of the pollen. The name 'pistil' is fre- quently applied to the carpel structures and is often a convenient name, although it is not an exact one. For example, each individual carpel may in certain cases be a pistil, a< in the butter- cup; while in cither eases several carpels may I r, ■ developed together as a single organ, which is also called the pistil, as in the apple. The term pistil, therefore, may be defined as any or- ganization of carpels which appears as a single organ with one ovary. 'Type Floweb' ami 'Modifications;' Sincethe structure of the flower is so extensively used as a criterion in classification, there has come to be iciated with it an enormous mass of technical terms, most, of which are of no value except, to the professional botanist. As the important ter- minology deals with the so-called 'modifications,' ill lie given in connection with a description cif the various relations which the floral membi i to one another, in the older morphology a so-called 'type flower' was assumed, and all variations from it were regarded as modifications of this type. This false conception in great measure has been abandoned, and flowers are recognized as having developed along many dif- ferent lines from exceedingly primitive condi- tions. For example, the flower of the lily was once regarded as a typical monocotyledonous flower, and all simpler forms were thought to be modifications of this type. The possible transi- tion from the flower of a lily to that of a grass has often been cited, the meaning being thai a grass-flower is merely a reduced lily-flower. The present view, however, is that the simpler grass- flower is more likely to be a primitive condition than a derived one. It is impossible as yet to distinguish all the lines along which flower- have advanced, and the relations of these lines to each other. Certain prominent lines are, however, conspicuous, and may serve as illustrations. In all of this evolution of flowers the end attained seems to be a better scheme for the transfer of pollen, chiefly by means of insects, or better de- vices for the scattering of seeds, or both. These conspicuous paths of advance may be summarized briefly as follows: Diversity of Flowers. In the most primi- tive flowers the parts have a spiral arrange- ment. For example, the sepals, petals, and stamens are not in definite rosettes or cycles, but appear at different levels and may be in- definitely repeated. In this case there is no such thing as definite numbers. In the more highly developed flowers, however, the spiral arrange- ment passes into the cyclic, in which the members of each set form a definite rosette or cycle, in which the numbers are limited. Usually these numbers are definite for great groups, the pre- vailing number in the cyclic monocotyledons be- ing three and the prevailing number in the cyclic dicotyledons being five or four. One of the com- mon causes oi diversity among flowers is the ab- sence of one or more of the four sets, or of some member or members in a single set. This may be the primitive condition of the flower, in which the given set or member is not to be expected ; or it may be a case of abortion or suppression, which means that organs which are to be expected have failed to develop, although they may do so par- tially. As prominent illustrations of such diver- sities the following may be mentioned. It fre- quently happens that but a single set of floral leaves appears, and it is customary to regard tin' missing set as the petals, such flowers being called 'apetalous.' In other case- neither calyx nor corolla appears, in which ease the llowcr is said to lie 'naked.' In still other ease- the stamens are lacking, anil if a pistil he present the flower is said to he 'pistillate.' If the pistil is lacking and the stamen- are present, 1 lie flower is 'staminate:' while if both stamens and pistils arc lacking, the flowers arc 'neutral.' Other diversities arise from the fact that the members of a Bel may to greater or lesser degree lose their independence and develop in common, giving the appearance of coalescence, for ex- ample, the sepals may organize an urn-shaped in' tubular calyx, or the' petals may organize a co- rolla which resembles a tube, a funnel, a hell. etc. The terminology used in such cases implies that members originally separate have coalesced; bu1 the fact is thai then- has been no coalescence of distinct parts, bui a ring-like outgrowth instead of