No. 591] HYBRIDISM IN ANGIOSPERMS 



137 



the blackbriar, and R. strigosus, the wild red raspberry, 

 both very variable species, the pollen is extremely bad. 

 Where these species occnr on islands, however, the pollen 

 is generally much more perfect, probably as the result of 

 isolation. I have noticed, for example, that R. villosus 

 and R. strigosus from Cape Breton Island have consider- 

 ably better pollen than that found in the case of conti- 

 nental material of the same two species. What is true of 

 these particular species holds more or less well for a 



large number of others of similar range and flowering 

 periods. Next may be considered a species of limited ge- 

 ographic range, namely R. deliciosus from the Kocky 

 Mountains. Here the pollen is practically entirely per- 

 fect, a few defective elements being occasionally found. 

 Last may be described R. odoratus, the so-called flower- 

 ing raspberry, which blossoms after the mass of other 

 species have shed their flowers. Here, as one might ex- 

 pect, the pollen is highly perfect and practically un- 

 mingled with shrivelled grains. A general study of the 

 Rosaca?, which can not even be summarized in the brief 



