Books and Current Literature 



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by means of which the light is caught and the interior is protected, 

 or in other species the individuals become as white as chalk, 

 so that the sun's rays are reflected. 



2. The species of the heaths occur on the inland sands, in 

 the Calluneta and in the Ericeta. The first are a sort of small 

 desert where the vegetation is very scarce and the lichens found 

 on them are almost the same species as those found on the dunes 

 In the Callunetum the growth of lichens depends largely on the 

 removal of Calluna, following which a rich vegetation of lichens 

 especially of Cladonia rangifera appears. In the more dry 

 Ericeta this species thrives even better than in the Callunetum, 

 but in the moister Ericeta all lichens disappear. 



3. The moors have no lichens as long as they are thoroughly 

 soaked, but as soon as they are dry enough for Calluna to grow 

 upon them the lichens invade the ground at the same time If 

 the heather is cut off they become dominant, but disappear as 

 soon as it grows up again. 



4. The lichens of the woods affect different kinds of trees, 

 apparently according to the mass of light which they suffer to 

 pass through their crowns and whether they are isolated or 

 growing together. Thus if a single spruce is left in the middle 

 of a wood, while all the trees around it are cut, its trunk will 

 be quickly covered with Lecanora. On young beech trees, which 

 keep their leaves during winter, no lichens thrive, nor do they 

 grow on the beech to any extent if it is planted in rich mould, 

 but if it is growing in acid and moor-like soil the trees will grow 

 more scattered and the trunks will be covered by a rich vege- 

 tation of bushy lichens. The oak has the greatest number of 

 lichens of all the trees of the forest on its trunk, 63 species being 

 enumerated. 



[ 5. In all, 138 species of lichens are enumerated as living 

 on rocks. None are found in Denmark on common chalk, but 

 on other sorts of limestone 36 species have been distinguished 

 Other facts which can not here be referred to, which are based 

 on thorough study of the lichens of Denmark in their habitat 

 relations, add to the value of this important pioneer work in a 

 field that has been but little cultivated. 



