314 



We find such statements in several authors, for example 

 in Koch (1892 p. 865), in Schenck (1886 a p. 92), who says that 

 M. spic. forms winter-buds, M. a. also probably. Birger (1908 

 p. 57) relies on Schenck's statements when he gives M. spic. 

 among the water-plants which form winter-buds further south, 

 but not in Harjedal. Sernander (1901 pp. 184 — 185) describes 

 hibernacula in both species ; in Schindler's diagnosis of M. spic. 

 (1905 p. 90) it is said "hibernacula adsunt", whereas they are 

 not named here for Ä1. a. In Ferdinandsen and Winge's cultures 

 of M. a. at a little below 18° C. (1909 p. 309) no winter-buds 

 were formed. Nor have I found them in this species, when I 

 investigated it in shallow water on the beach of Gurresø in the 

 middle of October 1909, and specimens from here, since cul- 

 tivated in a room not warmed, have not formed them either, 

 whereas they have been in slow growth through the whole win- 

 ter and obtained new, weak shoots. Glück (1906 p. 95) con- 

 cludes from his excursion observations and culture experiments, 

 that these two species are not at all able lo form hibernacula. 



That the formation of hibernacula might occur in nature 

 by combinations of conditions, which were perhaps not pre- 

 sent in experiments even of many different kinds, does not seem 

 impossible, just as that they sometimes appear, sometimes not, 

 dependent on the outer conditions probably, in these species 

 as in M. verticillatum, where the time for their formation 

 varies at different places in Denmark at least from August to 

 October. Goebel (1893 p. 361) even found that the formation 

 of winter-buds did not occur "owing to the assimilating activity 

 being too much reduced" at places which were much shaded, 

 but, it must be admitted, that the majority of the plants died 

 here "owing to the cold." 



It does not seem excluded that the above mentioned basal 

 leaves belonged to hibernacula, although on the other hand it 

 might well be thought, that the short, polar summer did not offer 

 conditions for their formation, even if we allow that they at all exist. 



