64 



Knud Jessen. 



p. 73). It is not, however, by any means all the flower- 

 buds that are formed which reach maturity. In Copenhagen 

 numerous dead buds were found during 

 autumn and winter. Otherwise such shoots 

 with a dead apical flower-bud behave as do 

 those that flower. The above-mentioned 

 weak shoots which do not at once produce 

 buds, may do so after having lived through 



Fig. 25. Dryas one Qr pg^^g several years of growth in 



octopetala. 



Median section through vi g°" r > but l als0 fmd that SUCtl »hoots may 



a young nower-bud which a f ter t h e i apse f a f ew years die in a purely 



would not have attained 



nie flowering stage until vegetative stage, probably suffocated by the 



the following summer . _ . _ 



(Kingigtok in vaigat; more vigorous shoots overshadowing them. 

 Aug. 2; «/!); c, ■ jj aglund writes that the short shoots im- 



dication of carpels ; st., 



young stamens ; P , petal; mediately put forth new short shoots, and 



sp, sepal. 



this is undoubtedly often true. I must 

 regard the short shoots in Dryas octopetala and D. inte- 

 grifolia simply as shoots which have become weakened by 

 competition among themselves, and it is undoubtedly normal 

 for the shoot-develop- 

 ment to end with 

 flower-formation. Ac- 

 cording to the above 

 the branch-system in 

 Dryas 1 is sympodial, 

 a few new shoots being 

 produced every year; 

 of these usually one or 

 two are more vigorous 

 than the others. 



The length of the 

 long shoots naturally 



Fig. 26. Dryas octopetala (Iceland). 

 16. 1. 1894. 



a A shoot-apex which shows how the rolling back of 

 the leaves increases towards the apex of the shoot ; 

 the uppermost leaves are living the older are dead ; 

 b, a leaf seen from the lower surface; c, a highly re- 

 volute leaf seen from the lower surface (Helgi Jôns- 

 son's figures 1. c). 



1 The North American and the North-east Asiatic Dryas Drumondii 

 Richards, behaves in a similar manner. 



