584 



THE AMERICAN NATURALIST 



[Vol. LI 



collected in Oregon, described what has proved to be the 

 same form under the provisional name Streptopus hrevi- 

 pes. KruJisea streptopoides then, although it agrees 

 with Streptopus in foliage and in fruit and seed char- 

 acters, differs remarkably in its flowers. They are very 

 small, the perianth nearly rotate, dark purple; the sta- 

 mens altered; and in the absence of a style the discoid 

 stigma rests directly on the ovary. It is possible that 

 connecting forms between KruJisea and Streptopus may 

 yet be found in Siberia, but at any rate the differences 

 between these two genera can not be reasonably sup- 

 posed to have arisen through natural selection. KruJisea 

 appears to have originated through a few definite ger- 

 minal changes and to have since been perpetuated by 

 heredity. 



Another pair of genera which is of much interest in 

 this connection is Plat jjstemon and Platy stigma, two Cali- 

 fornian genera of the Papaveraceae. Both occur abun- 

 dantly as spring flowers, occup\dng similar habitats. 

 Their main differences are as follows: 



Platy St emon Flaty stigma 



Stamens riimerous Stamens 6-12 



Filaments hroad and flattened Filaments narrower, flattened or 



These genera are almost exactly alike in habit, foliage, 

 pubescence, color of flowers and general form of the sta- 

 mens. They differ chiefly in the pistils, and these differ- 

 ences only become conspicuous as the seed capsules 

 mature. Platystemon has acquired numerous carpels 

 which are connivent or coherent in a circle. In develop- 

 ing, the carpels separate and their free margins cohere 

 with each other. Each carpel then becomes torulose by 

 constrictions between the seeds. How shall we account 

 for the origin of such a condition except tlirongh a marked 



