Rosaccæ. 



95 



it bears on both sides, especially on the veins, scattered uni- 

 cellular hairs. The outer wall of the upper epidermis is about 

 2.5// thick. The stomata occur only upon the lower surface 

 and are on a level with the surface. Palisade parenchyma 

 occurs in 1 — 3 layers. The proportion between the leal- 

 thickness (about: 155/«) and the thickness of the palisade tissue 

 was about |. The spongy parenchyma is loose. Fig. 36, A, 

 B, C, D. 



The structure of the leaf-stalk is as in Rub. saxatilis; 



Fig. 36. Rubus arcticus. 

 A, Transverse section of leaf. B, Epidermis of upper surface. C, Epidermis of lower surface. 

 D, Section of spongy parenchyma parallel to the surface. E, Portion of a transverse section 

 through an absorbent root ; end, endodermis ; hy, fungal hyphae, the innermost layer of 

 the cortex has highly thickened radical walls. F, Portion of a transverse section through 

 an aerial stem ; b, the bast outside the leptome ; c, cortical cells ; k, the cork-layer in the 

 rudimentary periderm p. A, li, 0, 1), E from Bosekop and F from Ångermanland m 

 Sweden. (A, D 190 ,',; B, C "" ,; F.. F »"/i). 



along the greater part of the length of the stalk there are 

 three bundles, and only along a very short distance, imme- 

 diately after the three bundles have emerged from the stem 

 there are 5 bundles. The stereom is very much as in Rub. 

 saxatilis. 



The flower-biology was first treated by Warming 



