430 MINNESOTA BOTANICAL STUDIES. 



Orchids is an indication of higher development and is a part 

 not found in the Cypripedinae. The essential point of differ- 

 ence is found in the column which is composed of three conflu- 

 ent stigmas all the other parts being to all purposes similar to 

 those of the other Orchids. 



The same conclusion is reached by S. LeM. Moore, who 

 thinks the "diandrous type an earlier one than the monan- 

 drous." 3 3 



Rolfe has exhaustively considered the subject in connection 

 with the Apostasiae.3 4 He believes that the Diandrae and 

 Monandrae evidently represent the two great diverging 

 branches along which the order has evolved, the more ancest- 

 ral Diandrae having developed but two marked tribes while the 

 highly specialized Monandrae have multiplied enormously and 

 given rise to several well marked tribes and a large number of 

 genera, all connected by a strong thread of affinity. The genus 

 Selenipedium has retained the ovarian characters of the more 

 ancestral Apostasiae while Cypripedium has a unilocular ovary 

 with parietal placentation as in the Monandrae. This cannot 

 of course be held to constitute any affinity with the Mon- 

 andrae, as Cypripedium clearly represents the culminating 

 point of development of the Diandrae. "The trilocular ovary 

 obviously represents the ancestral condition of the order, and 

 the development of the unilocular ovary with parietal placen- 

 tation in each of the two diverging branches may possibly be 

 an adaptation for saving room to accommodate the enormous 

 number of seeds produced." In discussing the arrangement of 

 the parts of the perianth, he makes Cypripedium arietinum R. 

 Br. the solitary exception in the genus, having all of the sepals 

 free to the base.^^ 



An additional point bearing on this question, is the ' ' singu- 

 lar fact, that though Cypripedium is one of the few tropical 

 genera of Orchids that inhabit both the eastern and western 

 hemispheres, it has not hitherto been found in Africa or Mada- 

 gascar, countries which have on plausible grounds been held to 

 have been the most recently peopled with plants. "^s 



Yet species have been reported from regions near the same 

 isotherm. C. Rothschildianum Reichb. is one of these forms, 

 being listed from the Malay peninsula and from New Guinea, ^ ' 



(33) Moore, S. LeM. Bot. Jahresb. 72 : 6. 1883. 



(34) Rolfe, R, A. Journ. Linn. Soc. Bot. 35 : 227. 1890. 



(35) Rolfe, R. A. Loc. cit. 230. 



(36) Hooker, .T. D. Curt. Bot. Mag. 116: 7102. 1890. 



(37) Hooker, .T. D. Loc. cit. 7102. 1890. 



