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in the younger roots, as mentioned above, both ectotrophie 
and endotrophie mycorhiza occur (Hesserman). 
C. 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. 
pee 
#3 
Fig. 9. Diapensia lapponica. 
Transverse section of root; highly mag. 
(Kangersuak.) 
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 
