80 Knud Jessen. 



records on the labels: The Greenland specimens are said to 

 be collected "under and between birch copses," consequently, 

 most likely on shady ground, while those from Iceland 

 grew on "Lien" (grassy slopes), consequently, probably 

 in more open ground. Leaves collected in very shady 

 localities in Denmark were about 90 ju thick and had in a 

 high degree the character of "shade leaves," with only one 

 layer of palisade-cells, which were fimnel-shaped, and a few 

 layers of spongy parenchyma. The proportion between the leaf- 

 thickness and the thickness of the palisade tissue was about 

 i in leaves both from Greenland and Iceland. The figures 

 show the leaf-structure of the common type; a loose palisade 

 parenchyma consisting of 2 layers of cells , about twice as 

 high as broad, and a likewise very loosely built spongy paren- 

 chyma. The stomata occur only on the lower surface of the 

 leaf; they are situated on a level with the surface. (Fig. 30, A, 

 B, C, D.) — Bast-tissue is absent from the leaf. 



Three distinct bundles enter the leaf-stalk (see p. 87); 

 shortly afterwards the two upper lateral ones divide each 

 into two bundles of which the lower one on both sides gra- 

 dually approaches the median lower bundle and ultimately 

 fuses with the latter the transverse section of which then 

 becomes crescent-shaped. The fusion takes place a short 

 distance above the point where the sheath ends, and in the 

 rest of the stalk there are 3 bundles. The two upper are 

 round in transverse section and lie in the ribs which form 

 the furrow on the upper surface of the stalk; the two latter 

 especially are accompanied by a strong fibrous tissue. 



The flower- biology has been in\^estigated by War- 

 ming (1886, b). He writes (loc. cit. p. 40) "The petals in the 

 latter (Rub. saxatilis) stand erect, and the stamens bend 

 somewhat toward the centre without however uniting so 

 closely together above it as in Rub. arcticus; there is, at any 

 rate in a somewhat older flower, an entrance between them 



