110 
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 trabecule 
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 SEGERSTEDT 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) (O. G. 
Perersen, 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 | 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. Lanrorss, 1907, p. 75. 
Of 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. 
