DEGENERACY OF FLOWERS. 271 



Where, however, insects are abundant, whether in high 

 latitudes or greater altitudes, as in the Alps, there two 

 causes will be at work to enhance the brightness of flowers ; 

 viz. insect stimulation and prolonged sunlight. For Sachs 

 has shown that the ultra-violet and invisible rays are 

 specially efficacious in the development of flowers; and as 

 the foliage grows more vigorously with prolonged light so 

 it is presumable that the flower-forming substances will be 

 more abundant as well.* 



The genus Plantago, like Thalictrum minus, Poterium, and 

 others, well illustrates the change from an entomophilous to 

 the anemophilous state. P. lanceolata has polymorphic flowers, 

 and is visited by pollen-seeking insects, so that it can be 

 fertilised either by insects or the wind. P. media illustrates 

 transitions in point of structure, as the filaments are pink, 

 the anthers motionless, and the pollen-grains aggregated, and 

 it is regularly visited by Bomhus terrestris (Delpino). On the 

 other hand, the slender filaments, versatile anthers, powdery 

 pollen, and elongated protogynous style are features of other 

 species indicating anemophily ; while the presence of a 

 degraded corolla shows its ancestors to have been ento- 

 mophilous. P. media therefore illustrates, not a primitive 

 antomophilous condition, but a return to it ; just as is the 

 case with Sa7iguisorha officinalis and Salix Caprea ; but these 

 show no capacity of restoring the corolla, the attractive 

 features having to be borne by the calyx, which is purplish 

 in Sanguisorha, by the pink filaments of Plantago, and by the 

 yellow anthers in the Sallow Willow. Plantago alpina is 

 self-fertilising, as the stigma does not wither until after 

 maturing the anthers. 



If we may speculate as to why some degraded flowers 



* Seo La Vegetation du Globe, par Grisobacli, t. i., p. 155 (trad. fran. 

 de Tchihatchcf). 



