XXV111 FIRST PRINCIPLES 



329. Pollen consists of vesicles or granules of cellular tissue, enclosing a mucous 

 substance, in which an iniinite number of exceedingly minute molecular bodies, 

 having a power of active motion, is contained. 



330. The function of the pollen is to vivify the ovula (344). 



331. For this purpose a granule of pollen which has fallen upon the stigma bursts, 

 and emits the mucus it contains, along with the active molecules floating in it. 



332. This mucus passes down the intercellular passages of the stigma and style, 

 and is finally conducted into the ovulum, through its foramen (408). 



333. In plants the ovula of which have no pericarpial covering (425), as Coni- 

 fers?, the molecules of the pollen are communicated to the ovulum without the inter 

 vention of any form of tissue. 



334. Each molecule produces one embryo, and usually but one is developed in 

 each ovulum ; but sometimes two or more accidentally develope, and then a seed 

 contains several embryos, as the Orange, the Onion, the Mistletoe. 



XIII. DISK. 



335. Whatever intervenes between the stamens and the pistillum receives the ge- 

 neral name of disk. 



336. It usually consists of an annular elevation, encompassing the base of the 

 ovarium, when it is sometimes called the cup ; Ex. Peeony. 



337. Or it appears in the form of a glandular lining of the tube of the calyx ; Ex. 

 Rose : or of tooth-like, hypogynous (312), processes ; Ex. Gesneria, Cruciferss : 

 or of a fleshy mass, upon which the ovaria appear to be seated ; Ex. Lamium. 



338. It is certain that the disk is sometimes a non-developement of an inner row 

 or rows of stamens, as is proved by the Moutan Peeony ; and it is probable that 

 such is generally its nature. 



339. But it is also probable that the disk is sometimes a mere cellular expansion 

 of the torus (300), as in Nelumbium. 



340. The disk is one of the parts which Linnsean botanists call nectary. 



XIV. PISTILLUM. 



341. The organ which occupies the centre of a flower, within the stamens, and 

 disk, if the latter be present, is called the pistillum. 



342. It is the fruit-bearing apparatus of flowering plants. 



343. It is distinguished into three parts, viz. the ovarium, the style, and the 

 stigma. 



344. The ovarium is a hollow case, enclosing ovula (354). It contains one or 

 more cavities, called cells. 



345. The stigma is the upper extremity of the pistillum. 



346. The style is the part that connects the ovarium and stigma. 



347. The style is frequently absent, and is no more essential to a pistillum than a 

 petiole to a leaf, or a filament to an anther. 



348. Sometimes the style is thin, flat, and membranous, and assumes the form of 

 a petal, as in Iris. 



349. The style is either articulated with the ovarium, or continuous with it. It 

 usually proceeds directly from the apex of the ovarium ; but in some cases arises 

 from the side, or even the base of that organ ; Ex. Alchemilla, Chrysobalaneae. 



350. Nothing is, properly speaking, stigma, except the secreting surface of the 

 style. Nevertheless, the name is often inaccurately applied to mere divisions of the 

 style, as in Labiata? : or to the hairy surface of undivided styles, as in Lathyrus. 



351. Sometimes the stigmas grow to the face of the anthers, which form them- 

 selves into a solid mass ; Ex. Asclepias. In this case the styles remain separate. 



352. The pistillum is either the modification of a single leaf, or of one or more 

 whorls of modified leaves. 



353. Such modified leaves are called carpella. 



354. A Carpellum is formed by a folded leaf, the upper surface of which is 

 turned inwards, the lower outwards, and the margins of which develope one or a 

 greater number of buds, which are the ovula. 



355. When the carpella are stalked, they arc said to be seated upon a theca- 

 phore, or gynophore ; Ex. Cleome, Passiflora. Their stalk is analogous to the 

 petiole of a leaf. 



356. The ovarium is the lamina of the leaf. 



