162 



and lower parts were on the verge of decay. The cork-layer 

 on these old stems is always thin and smooth. 



The peculiar, cricoid leaves of Empetrum occur sometimes 

 very closely together, as on the short, erect shoots, and some- 

 times at a distance (as much as 0"6 cm.) from each other, as 

 on the longer, creeping shoots. 



The leaves are functional for about three years, but may 

 persist for a longer time in a decaying and shrivelled-up 

 condition. When the Empetrum-iuus or mats, even at a great 

 age, present an abundance of leaves, this is due to the excessive 

 and dense branching which always occurs under favourable 

 conditions as regards shelter, etc. But in habitats where it 

 is exposed to the influence of a constant and strong wind it 

 assumes a very different appearance. Kolderup Rosenvinge (11, 

 p. 188) describes such wind-affected individuals from bleak 

 heaths in South Greenland. He writes that old plants present 

 "a green border which surrounds an inner part consisting 

 only of the old, crooked branches." "The green borders are 

 not developed all round, but only one side, in the form of a 

 somewhat irregular, almost semi-circular curve." All the curves 

 turn away from the direction of the prevailing wind. See 

 photograph from the Kitsigsut-islands (p. 189, Fig. 9). After- 

 wards Rosenvinge describes and figures such wind-affected tufts 

 of Empetrum (see p. 255 and Fig. 11) the leaves of which are 

 very considerably reduced in number, and in which the for- 

 mation of adventitious shoots is undoubtedly impossible on 

 account of the influence of the wind. 



The leaves on the shoot of the current year are obliquely 

 erect; on the shoot of the preceding year they are more 

 spreading and stand out somewhat at right-angles, and on 

 still older shoots they are usually twisted somewhat backwards. 

 They are orientated by the torsions of the extremely short 

 stalks so that they turn their surfaces upwards towards the light. 



Haglund (6, p. 31) mentions, that the leaves are consider- 



