323 



The short and brod obovate form 

 in the rosette of C. verna is strikingly 

 different from the linear one, which is 

 deeply submerged. 



In C. hamulata some of the emerged 

 leaves and the upper submerged are shortly 

 spatulate, below these longer spatulate 

 and sublinear ones are found, the narrowly 

 linear leaf closing the series (ßg. 16 and 12). 

 Most specimens of C. stagnalis have 

 typically broad leaves, yet diminishing in 

 breadth downwards, e. g. in plants from 

 a ditch at Vaags Ejde lake, the Færoes, 

 July 23, 1897 (C.H.Ostenfeld). The form 

 platycarpa Ktz. from deeper water has 

 not been found in the arctic material. 



The leaves of C. autumnalis as well 

 as those of other Pseudocallitriche are 

 uniform and linear. 



Most of the submerged leaves may be classed in the elodioid 

 type of Warming (1909 p. 182) or are somewhat longer. 



The apex of the leaf is in varying degree 

 emarginate; the two points are straight if 

 short, but converging if longer. More rarely 

 the leaf is almost evenly truncate (fig. 

 14 c, d). In the small leaves of the terres- 

 trial form of C. verna the apex is rounded 

 (fig. 13). 



Very deeply emarginate are the exceedingly 

 long and narrow leaves of С hamulata f. 

 trichophylla Ktz. (fig. He, /"), e. g. gathered 

 at Sukkertoppen 65°26' N. L. Greenland, and 

 at Bjørnedal near Ivigtut 61°13']N.L. Green- 

 land, moreover those of the robust, relatively 



Fig. 12. Callitriche 



hamulata Ktz. (X ca. 5) 



A upper leaf, 



B, С lower leaves. 



Fig. 13. Callitriche 



verna L. (X ca. 15). 



Terrestrial form. 



