1904 J 



l^rainerd, — Hybridism in the Genus Viola 



215 



This may be represented graphically by writing the five species, 

 as above, in equal spaces, and then drawing from the extremities of 

 these spaces straight lines obliquely upward to the right and to the 

 left. There will thus be formed ten squares, each of which may 

 represent the hybrid that might arise from crossing the two species 

 between the sides of the square produced downward. Thus, in the 

 diagram below, the square marked "a. c" would represent the form 

 obtained by crossing A and C ; i. e., V. affinis x septentrionalis. 







X 



a d \ y 



* * * ^v 





y 



Ac\ 



^ y^h. d. 



\ yc.e\. 



J 



A 



* * 



* * 



\/ * * * 



y^y- melissaefolia.^^ 



/ 



a. b. 



\ y/ 



b. c. N. y 



^c. d.\* *Xd. e.X 



^ 



* * 



7\* 



/ B \ 



\/ ' 



* * * \^/ * * * * ^^ 

 « * * * ^w V. Porteriana. ^^ 



Viola 





Viola 



1 1 



1 V. SEPTEN- 1 V. FiM- 1 Viola 



AFFINIS 





SORORIA 



1 TRIONALIS 1 BRIATULA 1 CUCULLATA 



Asterisks in the several squares indicate the number of different 

 stations in which the hybrid is believed to have been found ; from 

 which it would appear, if my conclusions are sustained, that out of 

 ten possible hybrids eight have actually appeared, and in most cases 

 more often than once. A somewhat detailed account of these eight 

 hybrids, of the associated plants, and of the circumstances attending 

 their discovery is herewith presented. 



I. Viola septkntrionalis x fimbriatula. A deserted clearing 

 on the mountain side above East Middlebury, partly covered with 

 blackberry bushes and young pines, has been a favorite station for 

 V. septentrionalis; and in the more open spaces were to be found 

 also numerous plants of V. fimbriatula. Here in the spring of 1902 

 I noticed in a tract of about four square rods a number of plants that 

 in leaf-oudine and in size and color of flowers were quite intermediate 

 between the two species just named. The cleistogamous fiowers and 



