Rosaceæ. 23 



old leaves and their remains. The older portions of the stems 

 appear ultimately to become bared (Warming's notes). The 

 prostrate floral shoots (Th. Wolf) are lateral (Fig. 7, ^4.); 

 their subtending leaves are often dead when they flower, so 

 that they arise from the stem below the terminal rosette. 

 The leaf-sheaths are large and closely folded around the 

 young leaves at the apex of the stem. I found no scale- 

 leaves. The much divided leaves are densely hairy especially 

 in Lange's /. humilis, the leaves of which bear long close-set 

 hairs on both sides, while his /. elatior is only slightly hairy 

 upon the upper surface. Lundager (1. c. p. 406) writes regarding 

 /. elatior that on Lille Snenæs in N. E. Greenland it was found 

 along river banks, and had very long roots which might reach 

 a length of 1.15 metre "and to a great extent were lying so 

 high that a portion of them lay bare." On the other hand, 

 he found /. humilis on gravel-banks exposed to the wind 

 and so greatly influenced by the sand-drift that they ac- 

 quired columnar forms, •'pillars," as shown in figures 7, B 

 and 8. 



Anatomy. The very slender absorbent roots con- 

 tain fungal hyphæ in the large-celled, few-layered cortex. 

 The epidermis dies early and collapses; the same happens 

 to large portions of the cortex with the exception of the 

 exodermis and the cell-layer outside the strong endoder- 

 mis. The structure of the exodermis is specially strong, its 

 radial walls, especially on the outside, being highly thickened 

 in the same manner as in Pot. emarginata. Secondary growth 

 in thickness begins early in the roots and also the formation 

 of periderm. Usually I found in the lateral roots a conti- 

 nuous woody portion with scattered vessels, but in these 

 roots the woody portion may also be divided into radiating 

 parts separated by broad non-lignified medullary rays. This 

 is what happens in the primary root, and owing to this struc- 

 ture and also on account of its considerable thickness (5 — 6 



