Rosaceæ. 



37 



shoot. Plants from Kekertak in Greenland collected Sept. 14 

 had formed flower-buds for the next summer, which had 

 developed so far that the exterior of the stamens was fully 

 formed and in the interior the mother-cells of the pollen- 

 grains could be seen; the carpels 

 were formed, but no indication 

 of the formation of ovules could 

 be observed. In the specimens 

 from Upernivik (May 17) the 

 young flowers were somewhat 

 larger; as yet no pollen was 

 to be seen, but in the carpels 

 the style was formed, and in the 

 ovules the embryo-sac could be 

 seen. 



The plants probably pass 

 the winter with dead leaves; in 

 Kekertak they had withered in 

 the middle of September 1886, 

 and in Upernivik they began 

 to unfold in the beginning of 

 June 1887. The shoot-apices are 

 protected by the leaf-sheaths; 

 scale-leaves are not developed. 



A n a t m! y. The struc- 

 ture of the slender absorbent 

 roots is shown in Fig. 15, F. The epidermis is very weak 

 and collapses, on the other hand the structure of the exoder- 

 mis is very strong especially in its radial walls. The rest 

 of the cortex consists of a few layers of cells in which balls 

 of fungal hyphæ occur; in the intercellular spaces fairly 

 vigorous hyphæ are found. In the secondary woody portion, 

 which begins to develop early, the medullary rays are absent 

 from the slender roots, but in the older roots broad, non- 



Fig. 14. Potentilla emarginata. 



A, Seedling from Lille Snenæs in N. E. 

 Greenland (25. 6. 1908 ; about ^k) ; the 

 cotyledons and the lower darkly shaded 

 leaves were dead and date probably 

 from 1906 and 1907 ; there are two 

 fresh leaves at the shoot apex ; the 

 primordial leaves have a simpler form 

 than the leaves of the full-grown plant. 



B, Leaf of a fnU-grown plant from 

 Spitzbergen ; somewhat reduced. (Drawn 



by Eu g. Warming.) 



