OF HOT A \ \ . WIS 



357. The style is an elongation of the midrib (174). 



358. The stigma is the denuded, secreting, humid apex of the midrib. 



350. Where the margins of the folded leaf, out of which the carpellum is formed, 

 meet and unite, a copious developement of cellular tissue takes place, forming 

 what is called the placenta. 



.'WO. Every placenta is therefore composed of two parts, one of which belongs to 

 one margin of the carpellum, and one to the other. 



361. As the carpella are modified leaves, they necessarily obey the laws of ar- 

 rangement of leaves, and are therefore developed round a common axis. 



362. And as they are leaves folded inwards, their margins are necessarily turned 

 towards the axis. The placenta, therefore, being formed by the union of those 

 margins, will be invariably next the axis. 



363. So that if a whorl of several carpella unite and constitute a pistillum, the 

 placentae of that pistillum will be all in the axis. 



364. The normal position of the carpella is alternate with the innermost row of 

 stamens to which they are also equal in number ; but this symmetry of arrangement 

 is constantly destroyed by the abortion or non-developement of part of the car- 

 pella. 



365. The carpella often occupy several whorls, in which case they are usually 

 distinct from each other; Ex. Ranunculus, Fragaria, Rosa. 



366. Sometimes, notwithstanding their occupying more than one whorl, they all 

 unite in a single pistillum ; Ex. Nicotiana multivalvis > Monstrous Citrons. In these 

 cases the placenta; of the innermost whorl of carpella occupy the axis, while those 

 of the exterior carpella are united with the backs of the inner ones, as must neces- 

 sarily happen inconsequence of the invariable direction of the placenta? towards the 

 axis. 



367. When the carpella are arranged round a convex receptacle (263), the exte- 

 rior ones will be lowest ; Ex. Fragaria. 



368. But if they occupy the surface of a tube, or are placed upon a concave re- 

 ceptacle, the exterior ones will be uppermost ; Ex. Rosa. 



369. This law will explain the structure of some anomalous pistilla, in which the 

 carpella are united into a confused mass ; Ex. the Pomegranate. 



370. Notwithstanding the formation of the placenta out of the two united margins 

 of a leaf, it often does not indicate any trace of such an origin ; but, in consequence 

 of non-developement, is sometimes reduced to a single point, bearing a single 

 ovulum. 



371. When the placentiferous margin is fully and regularly developed, it occu- 

 pies a line running down the inside of the cavity of a carpellum, and bears two dis- 

 tinct rows of ovula. 



372. If that part of the margin which is placentiferous is so small as to bear but 

 a very few ovula at or towards the upper part of the line of union, the ovula will 

 hang downwards within the cavity of the carpellum, and be either pendulous or sns- 

 pended. 



373. And if the placentiferous part of the margin be only at the lower part of the 

 line of union, the ovula will take a direction upwards into the cavity, and be either 

 erect or ascending. 



374. Whenever two carpella are developed, they are invariably opposite each 

 other, and never side by side. This happens in consequence of the law of alternate 

 opposition of leaves (160). 



375. When carpella unite, those parts of their sides which are contiguous grow 

 together, and form partitions between the cavities of the carpella. 



376. These partitions are called dissepiments. 



377. Each dissepiment is therefore formed of two layers. But these often grow 

 together so intimately as to form but one layer. 



378. Such being the origin of the dissepiments, it follows that, 



a. All dissepiments are vertical, and never horizontal: 



b. They are uniformly equal in number to the carpella out of which the pistillum 

 is formed : 



c. Thny proceed directly from the placentas : 



d. They are alternate with placenta; formed by the cohesion of the margins of the 

 same carpellum, and' opposite placenta? formed by the cohesion of the contiguous 

 margins of different carpella: 



e. A single carpellum can have no dissepiment whatever. 



