CLASSIFICATION OP MONOCOTYLEDONS 239 



fifth cycle in ordinary orchids the two lateral carpels form the 

 stigma, the anterior producing the disk-bearing " rostelhim," 

 while in Cypripedium all three carpels form the stigma. 



The origin of the Orchidaceae is very obscure. It is com- 

 mon to regard them as derived from the Liliales, but there are 

 many objections to this hypothesis. In any event, it seems 

 most natural to refer them to the same general stock. 



According to the views presented in this chapter, there are 

 three primitive monoeotyledonous stocks — Pandanales, Helobi- 

 ales, and Glumales — and thev are connected with the other 

 alliances as follows: Pandanales-Palmales-Synanthales; Helo- 

 biales-Arales; Glumales-Farinales-Liliales-Scitaminales-Orchi- 

 dales. 



