STIGMA AND PARIETAL PLACENTA IN PLANTS. 5G1 



divisions ; and it is further strengthened on considering 

 what takes place in Scilaniincce, wliere the same agreement 

 is found both in the pkicenta3 of tlie trilocular ovarium, 

 which in this family is the ordinary structure, and in the 

 unilocular, which is the excej)tion. 



I am aware that the agreement of Orc/ildcce with the [in 

 usual relation of parts in Monocotyledones is not admitted 

 by M. Achille llichard, nor by Mr. Lindloy, who has adopted 

 his hypothesis respecting the structure of the flower in this 

 family. According to M. Richard, the outer series of 

 perianthium is generally wanting, being found only in one 

 genns, Epistephium : the three outer divisions actually exist- 

 ing in the whole order, according to this view, become petals, 

 and the three inner divisions sterile petaloid stann'na. 



I have some years ago^ stated several objections to this 

 hypothesis ; at present I shall advert to one of those only, 

 considering it as conclusive ; namely, the position of the two 

 lateral stamina, which are generally rudimentary, but in some 

 cases perfectly developed, in this family. In several species 

 of Cyprip)edium , which is one of these cases of perfect deve- 

 lopment, I had then ascertained, by means of numerous 

 transverse sections made at various heights in the colunm 

 and at its base, that their vascular cords united with those 

 of the two lateral inner divisions of the flower, while that of 

 the third, generally the only perfect stamen, is manifestly 

 opposite to the anterior division of the outer series. The 

 position of stamina, therefore, so far from being regular, as 

 the hypothesis in question considers it, is absolutely without 

 example, tw^o of the inner series being opposite to two of 

 the supposed outer series of stamina. 



A very dificrent view respecting the formation of the 

 ovarium in Orchidece is that first advanced by Mr. Ikuicr 

 and adopted by Mr. Lindley, namely, that it consists of six 

 carpels, of which three, placed opposite to the outer series 

 of perianthium or sepals, are sterile ; the remaining three, 

 opposite to the imier series, or petals, being fertile, and 

 bearing their placentae on their axes or disks. 



Tlie chief argument in support of this view is no doubt 

 ' Liun. Soc. Trans, vol. xvi, p. C9S. {Afi/c, p. 5()L) 



;5G 



