87. Tlie placentas are developed at each of the two edges of 

 the carpellary leaf. If these edges be in their normal condi- 

 tions, that is, united, there will be apparently but one placenta 

 to the carpel, and that central. But if the edges be separate, 

 there will necessarily be two placentae to each carpel, the one 

 to the right and the other to the left of the dorsal suture and 

 style.) They are then said to be parietal {paries, a wall). 



FIG. 11. — 1, Cross section of a one-celled, three-carpelled ovary ■with parietal placentae, 

 the dissepiments partially obliterated ; 2, dissepiments wholly obliterated ; 3, dissepiments 

 obliterated, showng a free central placenta ; 4, a five-celled ovary with 5 false dissepiments, 

 as in the flax ; 5, vertical section of an ovary with parietal placentae ; 6, with free central pla- 

 centae ; 7, an amphitropous ovule ; 8, vertical section of the same ; a, funiculus ; b, raphe ; 

 e, chalaza; d, nucleus; e, secundine ; f, primine ; g, raicropyle; 9, anatropous ovules at- 

 tached to the ovary. 



88. But the placentaa are sometimes found in the common 

 centre when there are no dissepiments (Fig. 11; 3,6). This 

 anomaly, which is called a free centr il placenta, is thus ex- 

 plained. The dissepiments were at first actually formed in the 

 usual manner, but aftei-wards, by the rapid expansion of the 

 sheU, they were torn away and obliterated. 



a. As the ovules are always developed by the placentae, they, of course, grow 

 out of the margins of the carpellarj' leaf, and are, therefore, understood to be 

 analogous to budsij For, in the Bryophyllum, and some other plants, the true; 

 leaves do habitually develop buds at then- margins (Fig. 10 ; 8), and in the mign 

 ionette the ovules themselves have been seen transformed into leaves. 



89. The ovules are almost always enclosed in the ovary. In 

 the mignionette they are partially naked, and in the fir tribe, 

 Conifera?, entirely so, the carpellary leaf being open or wanting. 



