322 



Fig. 10. Callitriche hamulata Ktz. 

 (X ca. 150). 



Hairs from leaf and stem. 



C. vernit^ a land specimen from a dried-iip pool, Rude Ö 

 East Greenland c. 71° N. L., had 4 — 6 vessels in the upper 

 internodes; in a basin in the Botanical Garden of Copenhagen 

 5, in a part of the stem 15 — 7 internodes below the top. C. 



Iiamulata from iMiavevatn, 

 the F'ærOes, has 7, while 

 in the figure of Hegelmaier 

 (I.e.), only two are seen. In 

 C. stagnalis from Laugarne, 

 Reykjavik, Iceland, 16 are 

 found, in a part of the stem 

 furnished with stomata and 

 pith, indicating emerged 

 situation; Hegelmaier and Schenck mention, that 12 may be 

 found, which number was seen in a robust specimen from 

 Kunø, the Faeroes; the figures of Schenck and of Hegelmaier 

 show 7 and 1 1 in the land form, 4 

 and 7 in the aquatic form ( 1 886 b and 1. c). 

 Either very little pith is present 

 or in its place in the centre of the 

 stem, only a canal, the young pith- 

 cells, when only very few, having burst 

 with the stretching of the surrounding 

 tissue (Hegelm 1. c. p. 20). On an average 

 the pith is less resorbed in terrestrial 

 forms than in aquatic ones. 



The stem and both sides of the 

 leaves, in the species belonging to 



Eucallitriche, bear shield-shaped hairs (fig. 10), resembling those 

 of Hipjmris, abundantly on the air shoots or upper part of the 

 submerged ones, very few on the lower part. 



The opposite leaves connate at the base (fig. 11). 

 With exception of C. autumnalis, belonging to Pseudocalli- 

 triche, the species have polymorphous leaves with transitional forms. 



Fig. 11. Callitriche 



hamulata Ktz. (X ca. 10). 



Base of the leaves. 



