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The primary root-system consists of a comparatively strong 
primary root, sometimes striking deep and branching less 
abundantly, sometimes striking less deep and freely putting 
out horizontally-growing roots. Afterwards short, abundantly- 
branching, adventitious roots proceed from the ereeping shoot- 
systems, but these roots are comparatively few in number. 
Root-hairs are absent. Mycorhizas appear to be rare. 
Only in a few instances, e. g. in material from Iceland, did 
I find mycorhizas—short, club-shaped, and with numerons 
mycelium-threads projecting from the surface. 
In the first period of growth the primary shoot attains 
only a slight length and remains unbranched; in seedlings 
collected by C. H. Ostexrerv at Øfjord in Iceland, on July 30, 
1886, the epicotyl measured about 7 mm., while the hypocotyl 
and primary root together measured about 2°5 cm. It is pro- 
bable that the primary shoot does not branch until the second 
or third year. 
The lateral shoots of the young plant are transversely 
