The American Midland Naturalist 



PUBLISHED BI-MONTHLY BY THE UNIVERSITY 

 OF NOTRE DAME, NOTRE DAME, INDIANA. 



VOL. III. FEBRUARY, 1914. NO. 8. 



/%'" 



Proposed Segregates oj Viola. [ l^lj^a 'M'. 



BY J. A. NIEUWLAND AND R. M. KACZMAREK. 



The presence or absence of cleistogamous flowers in plants 

 has become more and more recognized as a basic character for 

 classification. The genus Crocanthemnm of Spach,' lately recog- 

 nized^ by Dr. Britton as the name applicable to our American 

 Rock Roses or Frostweeds has as perhaps its most important 

 character of distinction from Halimium and Helianthemum, the 

 presence of the less conspicuous cleistogamous flowers. In a closely 

 allied family, the Violaceae, in the genus Viola, these flowers 

 serve no unimportant part in differentiating species from one 

 another. As the presence or absence of them seems to be a constant 

 character in the plants mentioned we can see no reason why 

 further segregation of the old aggregate genus Viola may not be 

 suggested with reason, all the more as there are very important 

 characters of cleistogamous flowers, and the habit of the plants 

 in question demands serious consideration of the matter. In fact 

 vSpach and others before and after him without reference to presence 

 of cleistogamous flowers thought the various groups now aggregated 

 under Viola as sufficiently different from one another to constitute 

 natural genera. Even before Ivinnaeus and by some after him, 

 the Pansies were grouped by themselves. As already intimated 

 in a former article by one of us'' not only are these flowers present 

 constantly in some groups with other important differential 

 characters, and absent in others, but when present, there are 



1 Spach, E., Am. Sci. Nat. II. 6, p. 370, (1836); also Hist. Nat. Veg. 

 VI., p. 95, (1838). 



2 Britton, N. I.., 111. Fl. N. U. S. II., p. 539, (1913)- 



3 Nieuwland, J. A., Am. Mid. Nat. III., 3, p. 85-91. (p. 90). 



