STRUCTURAL BOTAJfT. 57 



talous corolla, and a one-celled compound ovary, with as 

 many lateral placentae, as there were carpellarj leaves, will 

 be the result. So it is in Helianthemum, in certain spe- 

 cies of Hypericum, and many other plants. Each of the 

 placeutse consists here of the contiguous margins of two 

 carpellary leaves, grown together. 



Finally we often meet with compound ovaries present- 

 ing one cell, a central placenta (placentae united), and no 

 dissepiments, as in Pinks, Primroses, etc. (PI. IV., 4c.) In 

 such cases we judge that the pistil was formed by the co- 

 alescence of several closed carpels (3 to 5 in Spergularia), 

 and that the dissepiments vanished very early. In some 

 or all pistils of this sort, the central placenta is regarded 

 by many botanists, and sometimes perhaps correctly, as a 

 growth from the axis or receptacle. 



107. Ovules are modified buds. Their number va- 

 ries from 1 to 100. "While Buttercups, Composites, and 

 Grasses have solitary ovules in their ovaries, in Ver- 

 bascum and Papaver they are indefinite — that is, not 

 readily numerable. 



As regards the position of the ovule in the cell of the 

 ovary (see Cut IX.), it is said to be erect when grow- 

 ing upward from the very bottom of the cell, as in the 

 Composites ; ascending (Fig. 1), when rising obliquely 

 from its point of lateral attachment; horizontal, when 

 projecting from the side of the cell, and not turning either 

 upward or downward; pendulous, when turned ob- 

 liquely downward ; and suspended, when hanging verti- 

 cally from the summit of the cell (Fig. 6). 



An ovule consists of a Tcernel, nucleus, and usually one 

 or two coats. In the upper part of the nucleus is the 

 embryo-sac, in which the embryo is formed after fertilisa- 

 tion ; and the coats— an inner one, tegmen, or secundine, 



