; 



128 



THE PISTIL. 



sides of the septa, and are called lateral placentae (Fig. 246). In others still, the 

 whole dissepiment is removed, and the placentae are placed near to the dorsal suture 

 (Fig. 247). 



Fig. 245. 



Fig. 246. 



Fig. 247. 



Fig. 245. Representing an ovarium with free central placentae. 



Fig. 246. Lateral placentae in the POPPY ; the centre being vacant. 



Fig. 247. Lateral placentae placed very near to the dorsal suture, as in the VIOLET. 



The source of the placenta is still a matter of doubt ; but it is either the termination 

 of the growing point, as Schleiden affirms, or it is a modification of the cells of the leaf 

 at the ventral suture. As the position of the placenta is the centre of the very extreme 

 end of the branch, and as it is the point of attachment and growth of the ultimate 

 organ of reproduction in plants, it is probable that Schleiden' s theory is both more 

 correct and more philosophical than that which has been more universally received. 



Before leaving this part of our subject we should state that the pistil is rarely, if 

 ever, transformed ; but occasionally it is itself a transformed stamen, as in the Horse- 

 radish (Cochkaria armoracid), and the House-leek (Sempervivum tectorum). 



The Ovule. Having now described the house provided by nature for the seed, 

 or embryo plant, we proceed to consider the organs for the protection and growth of 

 which it was designed. 



The ovule is the unripe seed, and consequently is the product of the organs of 

 reproduction in the plant. It resembles a leaf-bud in its function, and also in ita 

 structure, in so far that it has a central growing point and protective coverings ; and 

 in many instances, as the Mignionette and other plants, it has directly produced leaves, 

 without the intervention of a leaf-bud. 



The nucleus is the central growing point (Fig. 250, g), and consists of a mass of 

 cells, having the chemical constitution of albumen ; within it is a cavity containing 

 fluid called the amniotic sac and fluid (Fig. 250, A). It is formed at the earliest mo- 



Orthotropal. Campy lotropal. Anatropal. Amphitropal. Semianitropa 



Fig. 248. Representing the relation -which the base and apex of the nucleus bear to the hilum 



and foramen in the normal and abnormal conditions 

 The dot represents the foramen, the * the chalaza ; the outline is the primine, and the opening 



into it is the hilum at which the vessels enter. 



mcnt of the development of the ovule, and subsequently is inclosed in two coverings or 

 sacs, open at the top, the outer one of which is called primine (Fig. 250, c), and the 



