55 KANDA— VERBENA 1920] 



This work was carried on at the Hull Botanical Laboratory. 

 University of Chicago, under Professor Charles J. Chamberlain, 

 to whom I wish to express my sincere thanks for suggesting the 

 problem, and my appreciation of his kind advice throughout the 

 progress of the work. My acknowledgments are also due to 

 Professor John M. Coulter for his kindness in placing the con- 

 veniences of the laboratory at my disposal. 



Taxonomic observations 

 Although one can easily recognize the specific characters of the 

 original species, V. angustifolia, V. stricta, and V. hastata, it is 

 impossible to arrange the forms intermediate between them in a 

 linear series with regard to all of their contrasting characters. In 

 other words, all of the characters do not vary in the same direc- 

 tion, so that if one distributes them among the original species 

 with reference to one character, a 

 different distribution would be re- 

 quired for some other character. 

 Examples of the 3 species and the 

 6 intermediate forms which I was 

 able to collect are given in figs. 1-9 

 (pi. VI). Figs. 1,3, and 7 are V. 

 angustifolia, V. stricta, and V. 

 hastata respectively, and the others 

 are the intermediates arranged be- 

 tween the 3 species in accordance 



. . , . . . . ., Fig. 10. — Diagrammatic represen- 



with their degree of similarity to ^ of morphological re i a tionship 



them, as nearly as this COUld be between originals and intermediates. 



determined. I have attempted to 



represent diagrammatically the morphological relationship between 

 the originals and the intermediates by the triangle shown in text 

 fig. 10; the numbers on the triangle refer to the figures in plate VI. 

 The three apices (1, 3, 7) indicate the three original species, and 

 the points along the sides of the triangle show the probable posi- 

 tion of the intermediate forms with reference to them. For ex- 

 ample, 4 is believed to be nearer to 3 than to 7, and 5 is probably 

 about midway between 3 and 7. The contrasting characters of 

 all of the forms are given in detail in table I. 



