698 



^Yhich, var. proUfera, has by many authors been designated a separate 

 species, but which is most likely nothing but strongly proliferating 

 individuals, often loose and floating, growing in sheltered places. 



In other species, such as Rhodophyllis dichotoma , the thallus 

 becomes almost filiform when it grows at the bottom of fjords, 

 but may become a centimeter broad in the open sea, as mentioned 

 above. Kjellman has given a description and sketcli of tliis 

 peculiar narrow form (48, table XII, fig. 3). Exactly the same may 

 be said with reference to Euthora cristata, which, as mentioned 

 above, is robust with rather broad fronds in the open sea, whilst 

 these are almost filiform in fjords. According to Rosenvinge 

 (71, p. 227), similar conditions have been observed in Greenland. 



Other species are also more or less transformed in stagnant 

 water, e. g. Himanthalia lorea, the receptacles of which may be- 

 come irregularl}' swollen; Laminaria digitata, where the lamina, as 

 is well known, is split into a great many lobes, and which on ex- 

 posed coasts with rapid currents has a form known as f. stenophylla, 

 considered a separate species by many algologists, is often found in 

 places of stagnant water with its lamina undivided and more or 

 less sinuous and often urceolate in shape (f. ciicullata). The fronds 

 of Alaria esculenta and Laminaria saccharina likewise change ac- 

 cording to the habitat. A special form of the latter, f. linearis, is 

 found on exposed coasts and is remarkable for a narrow, but 

 thick and robust thallus (see fig. 85 of my flora), whereas its broad 

 forms, f. bullata and f. grandis, are found in sheltered places or in 

 deep water; Alaria too becomes broad in sheltered places without 

 currents (the narrow form from exposed coasts is drawn in my 

 flora p. 449, fig. 84). It is most peculiar, that similiar conditions 

 may act quite differently on different species of algae, as may be 

 seen from the preceding. I am unable to explain this satisfactoril}^ 



d. Temperature and Humidity of the Air. 



So far as the littoral algae are concerned, and especially in the 

 Faeroes where the littoral algal vegetation often reaches far above 

 the highest water mark, the warmth and humidity of the air are 

 naturally of great importance and may therefore be briefly men- 

 tioned here. 



With regard flrstly to the amount of heat, the average tempe- 

 rature is 6,5^ C. according to Willaume- Jantzen. January, the 

 coldest month, has a temperature of 3,2^, July, the hottest, 10,8^ C, 



