OROSS ANATOMY OF THE ANOIOSPEBMS. 311 



Compound Pistil — In compound pistils the coalescence maybe, 

 on tlie one hand, of closed carpels, and on the other of open carpels. 

 In the former case the pistil has generally as many loeuli (cavities or 

 cells) as there are carpels ; this is expressed by the terms bi-, tri-, 

 quadri-, and so on to muUi-locular (5 to 8, Fig. 210). Such pistils 

 have omie placentae — i.e., they are gathered about the axis of the 

 ovaiy. In the case of compound pistils formed by the coalescence 

 of open carpels the margins only of the latter unite, forming a 



Fio. 210.— Cross-sections of compound pistils : 1, 2, 3, 4, unilocular ; 5, 

 bilooular ; 6 and 7, trilocular ; 8, quaarilooular. 1, 2, 3, with parietal pla- 

 centsB ; 4, with a free central placenta ; 5 to 8, with axiie placentae. 



common ovary-cavity {unilocular, 1 , 2, 3, Fig. 210) ; here the 

 placentae generally occur along the sutures, and are said to be 

 parietal — i.e., on the walls. Between such unilocular pistils and 

 the multilocular ones described above there are all intermediate 

 gradations. In one series of gradations the placentae project 

 farther and farther into the ovary-cavity, at last meeting in the 

 centre, when the pistil becomes multilocular with axile placentse. 

 On the other hand, a multilocular pistil sometimes becomes uni- 

 locular by the breaking away of the partitions during growth. In 

 such a case the placentae form a free central column, commonly 

 called a free central palcenta (4, Fig. 210). In other cases a free 

 central placenta from the first occupies the axis of a unilocular but 

 evidently ploycarpellary pistil. In Anagallis, for example, the 

 placental column grows from the base of the ovary-cavity, and there 

 is at no time a trace of partitions. Here we may say that the parti- 

 tions are suppressed. 



Adna-tlon of the Gynoecium- — The gynoecium may be free from 

 all the other organs of the flower, which are then said to be hypogyn- 



