THE AM ERIC AX NATURALIST. [Vol. XXXVII. 



selective influence of the pollenizers, and regards the question of 

 its evolution as still unsolved. It is surprising that he does not 

 give more consideration to the influence of physiological, as well 

 as of ecological causes, in determining the particular colors of 

 flowers. In this genus, as in many others, it is the character of 

 the pigment-forming function, which is of chief importance. 

 On the Alps Muller found Tozzia alpina to be also a fly flower. 

 The corolla is bright yellow except that the three lower petals 

 are spotted with dark purple. In view of the fact that fly- 

 flowers are white, yellow, red and blue, the evidence that their 

 particular coloration has been determined by the color sense of 

 Diptera must be regarded as unsatisfactory. 



The species of Scrophularia are wasp flowers, green or 

 purplish without and brown purple and shining within. The 

 corolla is short and round with easily accessible honey. By far 

 the greater number of species of the Scrophulariaceae are adapted 

 to bees and many to bumblebees alone. The species of Linaria 

 are for the most part bumblebee flowers. L. vulgaris is bright 

 yellow with an orange-colored palate as a honey-guide, while L. 

 canadensis has small blue Mowers with a whitish palate. 

 Antirrhinum majus is bright purple or white with a yellow 



Chelone glabra (turtle head) is white with reddish lips. In 

 Maine this species is fertilized exclusively by bumblebees. C. 

 obliqua is bright rose color. Digitalis purpurea is purple with 

 dark purple spots within on the lower side. D. Intra is yellow. 

 Mclampyrum lincarc is whitish with the lower lip yellow. Other 

 species of this genus have bright yellow flowers. Pedicular is 

 with the flowers yellow and red is also fertilized by bumblebees. 

 Rhinanthus crista-galli (yellow rattle-box) is bright yellow with 

 the lower lip purple-spotted. 



In a preceding paper the capability of the calyx to develop 

 different colors was shown to equal that of the corolla. In con- 

 nection with the genus Castilleja the variety of coloring in the 

 floral bracts may be considered with advantage. In C. coccinea, 

 or the scarlet painted cup, the flower is greenish yellow and the 



