180 



Fr. J. Mathiesen. 



the left). This specimen was manifestly a self-pollinator, 

 but this species is, on the whole, as eminently suited for 

 cross-fertilization as our large flowered and dimorphic species." 

 Anatomy. Two-rayed adventitious roots occur (fig. 

 7, a), but the most common number of rays is 3 or 4. The 

 epidermal cells perish quickly, but their outer, and especially 

 their lateral walls are fairly resistant, so that well-preserved re- 

 mains of the original outer layer maybe seen even in older roots. 

 On juvenile roots, the cortical cells have somewhat thickened 



walls (according to Decrock, 

 a rather common feature of Pri- 

 mulaspecies). Strong thickenings 

 are especially noticeable on the 

 outer and, in some measure, also 

 on the lateral walls of the layer 

 of cells, directly under the 

 epidermis (fig. 7, a and c). These 

 thickenings, consisting of cellu- 

 lose, had disappeared in the root 

 of the preceding year (fig. 7, d). 

 The cells in the outermost layer 

 of the primary cortex fit closely 

 together and in close contact 

 with the epidermis, their walls 

 becoming somewhat cutinised 

 with age. The young roots contain some starch in their 

 cortical parenchyma. In the roots of the preceding year the 

 starch was almost exhausted, probably during the spring 

 growth, but I have found small single crystals of a calcium 

 salt, especially in the exodermis (fig. d). 



The rhizome has in all essentials the same structure 

 as in Pr. egaliksensis, but both Pr. sibirica and the following 

 species are characterized by having sclereids, singly or in 

 small groups, in the medulla of the rhizome. 



— ïi'^ 



Fig. 8. Primula sibirica. 

 Transverse section of a peduncle ; the 

 sector shows a vascular strand, stere- 

 ome and assimilation-tissue, together 

 with epidermis (obj. 4, oo.4). (Alten 

 Fjord. Norway.) 



