THE PISTIL. 



127 



Uie other ; and should the edges of the ventral suture be open at the point of develop- 

 ment of the placenta (Fig. 239), and closed at that of the stigma, there will be two 



Fig. 243. Fig. 244. 



Fig. 243. Showing two rows of carpels, one within the other. 

 e n.dicates the dorsal and d the ventral suture ; -whilst dis and the bracket mark the position and 



composition of the dissepiment or septum. The dorsal suture, e, of the inner whorl is opposed 



to the dissepiment of the outer whorl. 

 Fig. 244. Representing the alternate position of the dissepiments, or septa, with the placentae ami 



carpels in an ovary with three carpels, a ; 6, is the dissepiment, or the interval between the 



carpel and its boundary walls ; c, represents the ovules and placenta at the angle of the carpels, 



and separated from each other by the dissepiments. 



placentae to each carpel, and the latter will have a placenta on either hand. So, also, 

 should the stigma be double whilst the placenta is single, the two stigmas will be on 

 either hand of the placenta. 



As the dissepiments consist of the interval between the carpels, as well as of the 

 walls which bound it, and, in fact, lie between the carpels, they will be alternate with 

 the stigma, placenta, and carpels (Fig. 243). They will also be perpendicular or 

 longitudinal from the base to the apex of the leaf, and will be equal in number to the 

 carpels, at least when more than two carpels are present, and one carpel cannot have a 

 dissepiment. 



Various irregularities occur in the development, or subsequent growth, of the parts 

 of an ovary, and especially in reference to the placentae and septa. Thus, when the 

 placentae are not developed on the inner surface of the ventral suture, but upon the 

 outer surface that is to say, on the part looking into the space between the carpels 

 the septa and placentae will be opposite to and not alternate with each other ; and then 

 the placentae will be alternate with the stigma. Again, in many cases, as in the Poppy, 

 the Lychnis, and the Violet, the septa are imperfect, and do not extend from the dorsal 

 to the ventral suture. In the Lychnis the portion to which the placentae are attached 

 at the ventral suture remains, whilst the remainder is altogether removed \ and thus the 

 placentae, with a small portion of the septa, remain isolated at the centre of the ovary, 

 and are termed " free central placentae " (Fig. 245). In other instances the central 

 part, or the ventral suture alone, is reuv /ed ; and then the placentae are situated on the 



