XXX FIRST PRINCIPI.i 



379. It will also be apparent, that as the stigma must bear the same relation to 

 the dissepiments as the point of the leaf to the sides of the lamina, the stigma will 

 always be alternate with (between) the dissepiments. 



380. When the dissepiments of a many-celled pistillum are contracted so as 

 not to separate the cavity into a number of distinct cells, but merely project into a 

 cavity, the placentae, which occupy the edges of these dissepiments, become what 

 is called parietal ; Ex. Poppy. 



381. If the dissepiments af a many-celled pistillum are abortive or obliterated, 

 the placenta? remaining unaltered in the axis, a free central placenta is formed. 



382. A one-celled ovarium may also be formed out of several carpella, in conse- 

 quence of the obliteration of dissepiments ; Ex. Nut. 



383. All dissepiments whose position is at variance with the foregoing laws are 

 spurious. 



384. Spurious dissepiments derive their origin from various causes, and may 

 have either a vertical or horizontal position. 



385. When they are horizontal they are called phragmata, and are formed by the 

 distension of the placenta ; Ex. Cathartocarpus Fistula. 



380. If vertical, they either are projections from the back of the carpellum, as 

 in Amelanchier and Thespesia ; or they are caused by modifications of the pla- 

 centa 1 , as in Martynia, Didymocarpus, Cruciferre. 



387. Sometimes the apex of the pedicel extends beyond the base of the carpella, 

 rising up between them, and either forming an adhesion with the styles, as in Gera- 

 nium, or a central distinct axis as in Euphorbia. 



388. This elongation of the apex of the pedicel is more apparent in the fruit 

 than in the pistillum. It is analogous to the cellular apex of the spadix (259) of 

 Arum. 



389. The styles of different carpella frequently grow together into a solid cylin- 

 der ; Ex. Lilium. There are various degrees of union between the styles. 



390. The style is incorrectly said to be divided in different ways, in consequence 

 of this adhesion. 



391. If the ovarium adheres to the sides of the calyx it is called inferior, and 

 the calyx is said to be superior ; Ex. Apple. 



392. If it contracts no adhesion with the sides of the calyx, it is called superior, 

 and the calyx inferior. 



XV. OVULUM. 



393. The Ovulum is a body borne by the placenta (359), and destined to become 

 a seed (409.) 



394. It is to the carpellum (353) what the marginal buds are to leaves (154). 



395. It does not, however, appear to bear any other analogy to a bud than what 

 is indicated by its position. 



390. The ovulum is usually enclosed within an ovarium (344) ; but in Conifera? 

 and Cycadeaj it is destitute of any covering, and is exposed, naked, to the influence 

 of the pollen. 



397. It is either sessile, or attached by a little stalk called the funiculus, or »o- 

 dosperm. The point of union of the funiculus and ovulum is the base of the lat- 

 ter, and the opposite extremity is its apex. 



398. It consists of two sacs, one enclosed within the other, and of a vvch <us 

 within the sacs. 



399. These sacs arc called the primine and secundine. 



100. The primine, secundine, and nucleus, arc all connected with each other by 

 a perfect continuity of tissue, at some point of their surface. 



401. When the parts of the ovulum undergo no alteration of position during 

 their growth, the two sacs and the nucleus are all connected at the base (397) of the 

 ovulum. 



402. And then the base of the nucleus and that of the ovulum are in immediate 

 connexion with each other. 



403. But the relative position of the sacs and the base of the ovulum are often 

 entirely altered during the growth of the latter, so that it frequently happens that 

 the point of union of the sacs and the nucleus is at the apex (397) of the ovulnm. 



404. And then the base of the nucleus is at the apex of the ovulum. 



