Page:Encyclopædia Britannica, Ninth Edition, v. 4.djvu/154

Rh BOTANY [REPRODUCTIVE ORGANS. termed superior, as in Lychnis, Primula, and Geranium (fig. 215). When the margin of the receptacle is prolonged upwards, carrying with it the floral envelopes and staminal leaves, the basal portion of the ovary being formed by the receptacle, and the carpellary leaves alone closing in the apex, the ovary is inferior, as in Pomegranate, Apple, Pear, Gooseberry, and Fuchsia. In some plants, as many Saxifragaceoe, there are intermediate forms, in which the term half-inferior is applied to the ovary, whilst the floral whorls are half-superior. The style proceeds from the summit of the carpel, and may be looked upon as a prolongation of it in an upward direction (fig. 2G7). It is hence called apicilar. It consists not merely of the midrib but of the vascular and cellular tissue of the carpel, and when carefully examined is found to be traversed by a narrow canal, in which there are some loose projecting cells, a continuation of the placenta, con stituting what is called conducting tissue, which ends in the stigma. This is particularly abundant when the pistil is ready for fertilization. In some cases, owing to more rapid growth of the dorsal side of the ovary, the style becomes lateral (fig. 2GG) ; this may so increase that the style appears to arise from near the base, as in the Straw berry, or from the base, as in Chrysobalanus Icaco, when it is called basila). In all these cases the style still indi cates the organic apex of the ovary, although it may not be the apparent apex. When in a compound pistil the style of each carpel is thus displaced, it appears as if the ovary were depressed in the centre, and the style rising from the depression in the midst of the carpels seems to come from the torus. Such a style is yynobasic, and is well seen in Boraginacere and Ochnacese. The form of the style is usually cylindrical, more or less filiform and simple ; some times it is grooved on one side, at other times it is flat, thick, angular, compressed, and even petaloid, as in Iris and Canna. In Goodeniaceae it ends in a cup -like expan sion, enclosing the stigma. It may be smooth and covered with glands and hairs. These hairs occasionally aid in the application of the pollen to the stigma; and are called collecting hairs, as in Goldfussia, in Campanula, where they appear double and retractile, and also in Aster and other Composite. These hairs, during the upward develop ment of the style, come into contact with the already A Fig. 268. FIG. 266. L ni-ovular carpel of Lady s-mantle (Alchemitla) with the style s aris- iterally near the apparent base. It is called a lateral or scmi-basilar style. though it arises from the organic apex, which is here turned round. The stigma at the summit of the style is capitate. 267.--Compound syncarpous p stil of primrose (Piimn a). The five carpels of men it is composed are completely consolidated so as to appear one. The !?.! le sf -y l( : s aml stiS iiata *, are united. The flower is called mono- ripened pollen, and carry it up along with them, ready to be applied by insects to the mature stigma of other flowers. In Vicia and Lobelia the hairs frequently form a tuft below the stigma. The styles of a syncarpous pistil may be either separate or united ; when separate, they alternate with the septa. When united completely, it is usual to call the style simple (fig. 2G7) ; when the union is partial, then the style is said to be bifid, trifid, multifid, according as it is two- cleft, three-cleft, many-cleft ; or, to speak more correctly, according to the mode and extent of the union of two, three, or many styles. The style is said to be bipartite, tripartite, or multipartite, when the union of two, three, or many styles only extends a short way above the apex of the ovary. The style of a single carpel, or of each carpel of a compound pistil, may also be divided. Each division of the tricarpellary ovary of Jatropha Curcas has a bifurcate or forked style, and the ovary of Emblica officinalis has three styles, each of which is divided twice in a bifurcate manner, exhibiting thus a dich.otom.ous division. The length of the style is determined by the relation which ought to subsist between the position of the stigma and that of the anthers, so as to allow the proper application of the pollen. In some cases the ovary passes insensibly into the style, as in Digitalis, in other instances there is a Plate XI. marked transition from one to the other. The style may remain persistent, or it may fall off after fertilization is accomplished, and thus be deciduous. The stigma is the termination of the conducting tissue The stigm; of the style, and is usually in direct communication with the placenta. It may, therefore, in most instances, be considered as the placental portion of the carpel, prolonged upwards. In Armeria, and some other plants, this connec tion with the placenta cannot be traced. The stigma consists of loose cellular tissue, and secretes a viscid matter which detains the pollen and causes it to protrude tubes. This secreting portion is, strictly speaking, the true stigma, but the name is generally applied to all the divisions of the style on which the stigmatic apparatus is situated. The stigma alternates with the dissepiments of a syncarpous pistil, or, in other words, corresponds with the back of the loculaments ; but in some cases it would appear that half the stigrna of one carpel unites with half that of the con tiguous carpel, and thus the stigma is opposite the dissepi ments, that is, alternates with the loculaments, as in the Poppy. If the stigma is viewed as essentially a prolonga tion of the placenta, then there is no necessary alternation between it and the placenta, both being formed by the margins of carpellary leaves, which in the one case are ovuliferous, in the other stigmatiferous. There is often a notch on one side of a stigma (as in some Ilosacea.-), indicating apparently that it is a double organ like the placenta. To the division of a compound stigma the terms bifid, as in Labiatas, Composite, trifid, as in Polemonium, &c., are applied, according to the number of the divisions. When the divisions are large, they are called lobes, and when flattened like bands, lamella ; so that stigmas may be bilobate, trilobate, bilamellar, triktmellar, &c. It has already been stated that the divisions of the stigma mark the number of carpels which are united together. A quinquefid or five-cleft stigma indicates five carpels, as in Campanula, although tLs other parts are united. In Bignoniacea?, as well as i i Scrophulariacese and Acanthaccie, the two-lobed or bilamellar stigma indicates a biloculnr ovary. Sometimes, however, as in the case of the styles, the stigma of a single carpel may divide. It is probable that in many instances what is called bifurcation of the style is only the division of the stigma. In Graminea: and Composite there is a bifid stigma, and only one cavity in the ovary. This, however, may be probably traced to subsequent abortion in the ovary of one of the carpels. Its position may be terminal or lateral ; either on one side of the style, uni-