no 



occurs only in the Greenland specimens, I have not found any 

 features of importance which serve to distinguish the Danish 

 specimens from the Arctic ones. 



The young stem has a primary cortex consisting of large, 

 thin-walled cells, with a few thicker walled cells, and trabeculae 

 such as occur in the aqueous tissue below the central vascular 

 bundle of the leaf; a uniformly cuticularized epidermis; and a 

 large pith of similar structure to the cortex. The secondary 

 cortex, which according to Skgerstedt is developed on the lower 

 part of the year's shoot, consists of angular cells which have 

 become corky and contain starch. 



in regard to the formation of annual rings, where the new 

 annual ring begins, either a single tangential wall or several 

 in succession may be observed. The single tangential wall or 

 the outermost ones — in cases of several occurring in succes- 

 sion — collapse and form a continuous peripheral line. Where 

 several tangential walls occur, the latter are within the line in 

 question. I am not prepared to say whether these walls have 

 been formed during spring or in late summer. I am inclined 

 to believe that the latter is the most probable. Otherwise the 

 annual rings do not shew any special differences in the deve- 

 lopment of the summer and autumn wood (Fig. 24) {0. G. 

 Petersen, p. 77). As regards the structure of the stem I have 

 not found any differences between the Danish and the Northern 

 specimens in the material I have had at my disposal. 



I have not examined the roots. 



Lyonia calyculata (L.) Don. (Fig. 25.) 



Cassandra calyculata (L.) Don. 



O.G.Petersen, 1901, p. 76. Lidforss, 1907, p. 75. 



0Ï Lyonia I have had only a very small quantity of material — 

 a single sample from Finland — hence I have not been able to 

 enter more fully into this species. 



