330 



in terrestrial plants, but even in shoots which appear to have 

 been submerged, e. g. from Iceland (Aug. 24. 1894, Ol. Davidsson), 

 three fruits to one pair of leaves, i. e. two in one of the axils, 

 may be found. 



Some of the plants of C. hamulata (from Godthaab, West- 

 Greenland 64° I Г N. L. Septb. 31. 1907, dr. Søren Hansen) are 

 only 2 cm. long and yet fruiting; also in the small specimens 

 of C. autumnalis, ГЗ — 3-2 cm. long, from shallow water, only 

 с 0*33 m. deep, from a lake in West-Greenland (Hammersdal, 

 Disco 70° 9' N. L., M. P. Porsild) fruits are present. Irmisch 

 (1859 p. 354) observed flowers in the first pair of leaves of С 

 verna, both on the primary stem and on the shoot 

 from the cotyledonary axil. 



As a rule all parts of the quadrisulcate separating 

 fruit have been developed, all of them containing 

 an embryo (fig. 19). Sometimes only two or three 

 parts have been developed, e. g. in C. stagnalis 

 Fig. 19. from Laugarne (at Reykjavik, Iceland, C. H. Osten- 



a iricie ^^^^ ^ .^ 1895) this is rather common. 

 verna L. 

 (X ca. 16) The material of С autumnalis being very small 



Embryo. g^^^ Qjjjy herbarium specimens, only a few fruits 

 have been examined; some of these contain three embryos; 

 thus they do not correspond to v. hmuUfera Norm, from the 

 farthest North (Hartman p. 383) with only two separating fruits 

 developing. Judging from the abundance of well-developed 

 embryos, seedlings should be expected to be very common; 

 Hartz (1895 p. 278) found C. venia ß minima only as seedlings 

 in the middle of July in an early ice-free lake on Danmarks 

 70° 27' N. L., East Greenland. Some of the specimens of 

 the material are seedlings. 



But vegetative propagation is probably frequent in the far 

 North as well as in the temperate zone, where (Sernander 1901 

 p. 157 etc.) many shoots are set free all the year round in 

 water free of ice. 



