STIGMA AND PARIETAL PLACENTAE IN PLANTS. 561 



divisions ; and it is further strengthened on considering 

 what takes place in Scitaminece, where the same agreement 

 is found both in the placentae of the trilocular ovarium, 

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

 unilocular, which is the exception. 



I am aware that the agreement of Orchidece with the [in 

 usual relation of parts in Monocotyledones is not admitted 

 by M. Achille Richard, nor by Mr. Lindley, 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 5 

 genus, Epistephium : the three outer divisions actually exist- ^, 

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

 and the three inner divisions sterile petaloid stamina. 



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 Cypripedium, 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 column 

 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, two of the inner series being opposite to two of 

 the supposed outer series of stamina. 



A very difi'erent view respecting the formation of the 

 ovarium in Orchidew is that first advanced by Mr. Bauer 

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

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

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

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

 bearing their placentae on their axes or disks. 



The chief argument in support of this view is no doubt 



' Linn. Soc. Trans, vol. xvi, p. 698. {Ante, p. 501.) 



36 



