1 92 1. No. 7. STUDIES ON THE LICHEN FLORA OF NORWAY. 7 



the more alpine C. /iiascrns, not to speak of C. nivalis, so plentiful on the 

 mountains throughout the whole of the country. 



Its best station is the light hr forest (Pinits silvcstcrj, accordingly it 

 is most general on inland hr heaths (Norw. furumo), and in some coast 

 fir forests on primitive rocks. Yet even there it is chiefly restricted to 

 open places, roadsides, and the like; it is a heliophilous species. 



I have never seen it more abundant than at 'Hensmoen' near Hene- 

 foss, and at 'Modumsmoen' between Modum Bath and the railway-station 

 Gjeithus (both places fir forests on sandy ground). 



It requires a exhausting work to estimate the quantity found in any 

 given forest. It never covers large continuous areas. On small areas, 

 0.25 m^ or the like, a weight may be collected which corresponds to 

 550 kg. air-dried (= about 1450 kilos water-saturated) lichen per 1000 m-. 

 But it would be difficult to find 5 or 10 m- covered with Cetraria islandica 

 of this quality, and absolutely imposible to find 100 continuous m-. 



The average quantity per m- is much beneath this sum. The time 

 at my disposal was insufficient to acquire decisive result for the whole 

 forest, but after the experiments made, I do not venture to put the average 

 weight higher than at 710 kg. air-dried 'moss' per 1000 m-. And this 

 small forest is one of the richest stations in Norway. 



The time necessary to collect a certain weight will depend upon 

 circumstances. At Hensmoen 3 zealous boys (12 — 13 years old) collected 

 3600 gr. (all weights = dry weight) with their hands in 13 minutes. This 

 is about 100 gr. a minute for each boy, which is supposed to represent 

 the maximum weight that can be collected on an abundant spot. On a 

 common Cetraria field a boy will perhaps be able to collect 4 — 5 kilos an 

 hour. — But places where so much can be collected are few and small 

 in area, and the 'crop' will soon become exhausted. 



A much larger harvest might be obtained by using implements (a rake 

 or a fork) but this would also give disproportionate admixtures (pine-needles, 

 earth) which are not easily removed. When the 'moss' dries, a certain 

 part of the admixtures will, however, fall to the ground. 



The lichen mass is air-dry when it has been placed so long on the 

 floor of a warm and well ventilated room that it does not loose more in 

 weight. Air-dried Cetraria islandica contains about 14 — 15 ^/0 water, 

 saturated about 60 — 7 o g. This species retains its moisture much better 

 than Cladonia alpestris. After rain, the latter species dries up in a few hours, 

 if there is sunshine and a dry wind. This fact may be of some importance 

 for the relatively quicker growth of the former species. 



I is no easy task to remove the poisonous acid by methods which 

 are fit for technical use. The bread and dishes prepared were edible, 

 but on the whole the results were not proportionate to the laborious pro- 

 cesses of collecting and preparing. 



