252 ESSENTIAL ORGANS — THE OVULE. 



and destined to become the seed. It bears the same relation to the 

 carpel that marginal buds do to leaves, and when produced on a free 

 central placenta, it may be considered as a bud developed on a branch 

 formed by the elongated axis. The single ovule contained in the 

 ovaries of Compositae and Grasses may be called a terminal bud 

 surrounded by a whorl of adhering leaves or carpels, in the axil of 

 one of which it is produced. In Delphinium elatum ovules some- 

 times appear as mere lobes of the carpellary leaf; in Aquilegia ovules 

 ■ transformed into true leaves are occasionally produced on either 

 margin of the carpel ; and the ovules of Mignonette sometimes assume 

 the form of leaves. In such cases the vascular bundles of the placenta 

 (pistillary cords) are formed by the lateral veins of the carpellary leaf. 

 These veins pass into the marginal lobes or leaflets which represent 

 ovules, and seem to prove that the placenta, in such cases, must be 

 truly a carpellary, and not an axile, formation. 



The ovule is usually qontained in an ovary, but in Ooniferse and 

 Cycadaceee it is generally considered as having no proper ovarian 

 covering, and is called Tiaked, these orders being denominated gymno- 

 spermous (yvfivbg, naked, and ffTsg/ia, a seed), or naked-seeded. In 

 these orders the ovule is produced on the edges, or in the axil of 

 altered leaves, which form no evident style or stigma. The scales of 

 the cones in Coniferse are by some looked upon as the homologue of 

 opened-out carpels bearing exposed ovules. In the common Fir 

 there are usually two ovules at the base of the upper surface of each 

 scale. In the Juniper each scale bears one ovule. Ih the Cypress 

 the scales are peltate, and cover numerous ovules ; while in the Yew 

 there is a solitary ovule at the apex of a cone-like organ formed 

 by numerous barren scales. In Gnetaeese there is also a solitary 

 ovule, the secundine of which is pushed out into a long tube-like 

 process. In Oycadacete the ovules are either produced on the edge of 

 altered leaves, which some have called leaf-like carpels, as seen in 

 Cycas, or, as in Zamia, they are covered by peltate scales, from the 

 summit of which they are suspended. The Gymnospermal view is not , 

 supported by all botanists ; some maintain that there is a true ovarian 

 covering independent of the scales, and others think that the outer coat 

 is of the nature of a disk. The subject is still under discussion. The 

 carpellary leaves are sometimes united in such a way as to leave an 

 opening at the apex of the pistil, so that the ovules are exposed or 

 semi-nude, as in Mignonette. In Leontice thalictroides (blue cohosh) 

 the ovary ruptures immediately after flowering, and the ovules are 

 exposed. So also in species of Ophiopogon, Peliosanthes, and Stateria. 

 In the species of Cuphea the placenta ultimately bursts through the 

 ovary and corolla, becoming erect, and bearing the exposed ovules. 



The ovule is attached to the placenta either directly, when it 

 is called sessile, or by means of a prolongation called a funiculus 



