STIGMA AMJ I'AIUKTAI; I'J^ACKN'JVE IN PLANTS. 551) 



being obviously so in ajiiiiy cases ; iind in one genus at least, 

 Ihsniannia, it extends nearly the whole length of the ova- 

 rium, so as to be coiiiinensurate with and placed cxactlv 

 o])])osite to the internal polyspernions ])lacenta. 



That the stigma is always double aj)i)cars probable t'loni 

 those cases in which it is cither completely developed, as in 

 the greater part of Gramincce where the ovarium is sim[)le ; 

 in the compound ovarium in Urnia ; and from those in which 

 the development, though less complete, is still sutticiently 

 obvious, as in many I'Jffp/iorbiacece and in several Tridece. 

 This degree of development, however, is comjjaratively rare, 

 conliueiice between the two stio-mata of each cai'pel beiufj 

 the more usual stiucture ; and in the compound pistillum a 

 greater degree of confluence often takes j)lace in the stigmata 

 than in the placentic; — a fact, which in all such cases is 

 obviously connected with adaptation of surface to the more 

 complete performance of function. 



Another difference frequently occurs between the mode of 

 confluence of placentae and stigmata, namely, that in the 

 compound but unilocular ovarium, while the placentte of the 

 adjoining carpels are united, the stigmata of each car[)el are 

 generally confluent. But this rule admits of exceptions, as 

 in Parjia-stiia, in many Cruci/erce, and in Papaccrcuece ; in all 

 these cases the stigmata as well as placentae of the adjoin- 

 ing carpels are confluent, a structure satisfactorily proved in 

 i'ruL'iferce by several cases of monstrosity, in which the 

 stamina are transformed into pistilla; and in Papavcracece 

 by a series of modifications of structure as well as by a like 

 transformation of stamina. 



A similar confluence of stigmata in the compound mul- 

 tilocular pericarpium is of nuich rarer occurrence; it is 

 foiuid, however, in the majority of Iridece, in which the three 

 stigmata alternate with the cells, and consequently with the 

 placentae of the trilocular ovarium. Tliat this is the correct 

 view of the composition of the stigmata in Tridece is at least 

 probable from their occasional deep division, and more par- 

 tictdarly still from the bifid petal-like styles or stigmata 

 which are op})osite to the cells of the ovarium in other genera 

 of the same familv, as in Iris and Monca. In both these 



