THE PISTIL. 



125 



direct attention to this interesting but difficult subject ; and in doing so shall conb.de 

 the pistil as a whole. 



If we take up any oval sharp-pointed leaf, such as that of the Poplar, and fold its 

 edges together, so as to inclose the upper surface, 

 we shall have the mode of construction of the 

 ovary. It will then present an internal cavity 

 without any partitions, bounded on each side by 

 a plate or valve, which is the half of the lamina 

 on each side of the midrib. There will also be 

 two lines of union, or sutures, one on the back 

 formed by the midrib, which in the leaf naturally 

 unites the two sides of the lamina, and the other 

 in front, formed by the union of the edges of 

 the leaf. The former line of union is called the 

 dorsal, and the latter the ventral suture. Each 

 ovary will thus have an expanded base and a 

 narrower apex, with a single cavity, two lateral 

 pieces or valves, and a dorsal and a ventral 



suture lying between them. Such an ovary 



* c and d represent u single and double car- 

 is termed simple ; and as it develops the placenta 



pel, with a and b to illustrate the mode 

 of construction out of a leaf. The lower 

 expanded portion is the ovary, and the 

 free upper end the stigma. There are 

 two carpels ; they face each other at d 

 and b. e, the ventral suture ; /, the 

 dorsal suture. 



upon the inner edge of the ventral suture, the 



placenta will be partly attached to one side and 



partly to the other, and thus be double. So, in 



like manner, with the stigma above mentioned ; 



it is situate at the extremity of the midrib, on the ventral suture, and will be formed 



by both sides, and consequently be double. The style, when it exists, will have, on its 



dorsal aspect, the vascular structures belonging to the midrib ; and on its anterior or 



ventral part, the new tissue described as the conducting tissue (Fig. 228), which will 



either be a mass of placentas or a prolonged placenta. Thus the stigma, conducting 



tissue and placentae, occupy the ventral suture ; whilst the vascular tissues are formed 



at the dorsal suture. 



This description will apply equally to an ovary, which consists of many such leaves, 

 so far as each separate leaf or carpel, as it is then termed, is concerned, provided the 

 development of each part proceeds normally. But something further must be said in 

 reference to the arrangement of the leaves or carpels. 



If the various carpels are so situated that they are not connected with each other, 

 the ovary is called Apocarpus (Fig. 240) ; but if, as is usually the ease, they are closely 

 and indissolubly associated, the ovary is said to be Syncarpous (Fig. 241). "When only 

 two carpels are formed they may be placed side by side, that is, with their ventral 

 sutures having the same direction ; or facing each other, when the same sutures will 

 regard each other (Fig. 239). If three or more carpels are formed, they will, in obedience 

 to a general law, be placed in a whorl, and consequently have all their dorsal sutures 

 directed outwards, and their ventral sutures directed inwards, or towards a common 

 centre. As the carpels will thus be placed side by side, there will be spaces, however 

 small, between them ; and thus there will be alternately a carpel and a space (Fig. 243). 

 The space will be bounded by a carpel on either hand, and may therefore be said to 

 have double walls. The space and the boundary walls are together called the dissepi- 

 mentt, or septa ; and when the carpels are united into one mass, the whole may bo 



