SUMMARY. 67 



trichomes. Should each kind of trichome represent a distinct character, 

 as seems possible, we have here several methods by which unit characters 

 may take their origin. 



(7) \T\Juglans there is no direct relation between the size or vigor of 

 the leaves or plant and the size of the trichomes, although position on 

 the leaves directly affects size and form of the trichomes. 



(8) In the second generation of Juglans calif arnica X Jug Ian s nigra the 

 short secreting trichome, in size and form, reverted to nigra. No other 

 case of reversion to one pure line, of a character of trichome common to 

 both pure lines, was observed \njng/ans. 



