153 



In the younger roots, as mentioned above, both ectotrophic 

 and endotrophic mycorhiza occur (Hesselman). 



С. Summary. 



With regard to its flowers, Diapensia lapponica is ento- 

 mophilous, slightly protogynous or homogamous with, however, 

 a tendency to self-pollination. 



its oecological form is decidedly xerophytic. 



Fig. 9. Diapensia lapponica. 



Transverse section of root; highly mag. 

 (Kangersnak.) 



Anatomically it is only the leaves which are of xerophytic 

 structure, as it is only these organs which come into direct 

 contact with the atmosphere. The xerophytic structure is there 

 indicated by the thick membranes and cuticle of the upper and 

 lower epidermis, and by the great development of thick-walled 

 cells in the spongy parenchyma. The structure of the leaves 

 is not as xerophytic as that of the leaf of Rhododendron lap- 

 ponicum, but approximates to the degree of protection presented 

 by the latter species. Perhaps, owing to the tufted, low-growing 



