331 



If cultivated they grow and roots are developed even on 

 very small pieces. "In C. auturnnalis the vegetative propaga- 

 tion might be less important than in the other species. The 

 vegetative shoots, however, with their air-channels act as an 

 excellent floating apparatus for the heavy fruits, which, if isola- 

 ted, immediately sink to the bottom. Within the other species 

 too the fruits are generally carried with the mother-plant" 

 (Sernander). Kølpin Ravx had also observed (1894 p. 178), that 

 the fruits of C. autmmialis were unable of themselves to float. 



Thus their wings are in that respect of no use. 



Isolated seedlings of C. stagnalis were found among the 

 flotsam in the course of the summer in Sweden (Sernakder 1. c. 

 p. 157 and 82). 



Summary. 



As was to be expected the plants examined, being aquatic 

 plants, show no morphological or other peculiarities except in size, 

 which could with certainty be referred to arctic conditions. Aquatic 

 plants as is well known are subject to great variations, such 

 variations being very dependent on external conditions, pro- 

 bably mainly of a nutritious nature, as has especially been poin- 

 ted out by GoEBEL (1893, 1908 etc.i and Küster (1903). This 

 being granted, it seems natural, that these variations largely 

 depend on light conditions, — seen for instance in the dif- 

 ferences between specimens from deep and from shallow water — , 

 because of the assimilation which does not preclude the light 

 from also in other ways having effect on the variations. 



Thus, the numerous small differences met with may be 

 due only to local circumstances. 



But in size the specimens from Greenland are on the whole 

 smaller, both those of Hippuris, Myriophyllum and Callitriche 



