123 
about the same size as those in the palisade-tissue. No aqueous 
tissue occurs, nor is the stereom especially well-developed. 
In the material I had for investigation no difference could be 
observed between the Danish, the Subarctic and the Arctic 
specimens. But here, as was the case with regard to the other 
species, the material was too scanty to be useful for the 
investigations in question. The specimens from Furca Pass, 
Switzerland (Aug. 1904; H.E.P.), did not shew any differences 
of importance. 
The stem. According to Tenin (1892, p. 74) the primary 
cortex consists partly of transparent, thin-walled cells containing 
water and partly of thick-walled cells which contain chlorophyll 
and occur partly in trabecule and partly in groups (cf. e. g. 
Ledum). It persists for about three years. The secondary 
cortex, according to SEGERSTEDT, consists of an ordinary cork- 
tissue. 
The spring wood is differentiated from that of the summer 
(or autumn); but the limits of the annual rings are not always 
sharply defined. According to Simon (1902) the cause of the 
distinctness of the annual rings in Vac. Vitis-idea, and of the 
differentiation of the wood of the different seasons as mentioned 
above, will be found in the fact that evergreen forms require 
more stereom, while the deciduous forms need relatively more 
L 
‘“Speichergewebe ;” but this is scarcely to be regarded as a 
universal rule (cf. Ledum, Rhododendron, etc.y. 
The roots I have had for examination from Hovmose in 
Gadevang at Frederiksborg shewed both endotrophic and ecto- 
trophic mycorhiza. 
Vaccinium uliginosum L. (with f. microphyllum Lge.) 
(Figs. 34—37.) 
Boreesen, 1895, pp. 236—237. SEGERSTEDT, p. 25. AMBRONY, 
1890, p. 71. O.G. Petersen, 1901, p. 81. Hesserman, 1900, p. 27. 
Maury, 1887, p. 105. 
