822 ZONES AND REGIONS [Pt. Ill, Sect. V 



colour, and subsequently found in the snow on Mont Blanc and Pichincha ; 

 and Scytonema gracile (Cyanophyceae), which occasionally forms the chief 

 constituent of the ice-vegetation in the interior of Greenland. 



In addition to the Algae, Wittrock succeeded in discovering in the 

 vegetation on ice and snow microphytes devoid of chlorophyll, in particular 

 Chytridium Haematococci, Al. Br., which is parasitic on Sphaerella nivalis. 

 Finally, a few moss-protonemata, which in no instance had developed into 

 leafy plants, were occasionally observed. 



Wittrock's list, which however concerns only Scandinavia and the Arctic 

 zone, though it included all the then known plants growing on snow and 

 ice, has very recently been supplemented by Lagerheim, who, as the dis- 

 coverer of red snow on Pichincha, determined three hitherto unknown species 

 of Chlamydomonas, namely C. sanguinea, C. asterosperma, and C. nivalis, 

 which however, according to Chodat, are only stages of the polymorphous 

 Sphaerella nivalis. In company with the red Algae two other unicellular 

 Algae appeared, the already mentioned Ancylonema Nordenskjoldii and 

 Raphidium nivale (Lagerh. sub Raphidonema) (Pleurococcaceae), which has 

 since been found by Chodat in the snow of Mont Blanc (Fig. 502, 4) ; also 

 a unicellular fungus, Solenotila nivalis, Lagerh., which exceeded the Algae 

 in number of individuals. The total number of snow-plants on Pichincha, 

 according to Lagerheim, amounts to twenty-four species, which belong 

 to the Cyanophyceae, Diatomaceae, Desmidiaceae, Volvocaceae, Tetra- 

 sporaceae, Pleurococcaceae, Chytridiaceae, and Musci (protonemata), and 

 thus, excluding Solenotila as being of problematic systematic position, 

 belong to the same groups as snow-plants of the Arctic zone and of the 

 mountains of the temperate zones. 



The oecology of the vegetation on snow and ice has not yet been investi- 

 gated. 



SELECT LITERATURE. 



Agardh, C. A. I. Memoir on the Red Snow brought from the Polar Regions. English 



transl. in Greville, Scottish Cryptogamic Flora. Vol. IV. 1826. Plate 231. 



II. Systema Algarum. Lundae, 1824. 



Apstein, Carl. Das Siisswasserplankton. Methode und Resultate der quantita- 



tiven Untersuchung. Kiel und Leipzig, 1896. 

 Berggren, S. Alger fran Gronlands inlandsis. Ofversigt af Kongl. Vetenskaps 



Akad. Forhandlingar. Jahrg. XXVIII. Stockholm, 1872. 

 Bornet, Ed., et Flahault, Ch. Sur quelques plantes vivant dans le test calcaire 



des mollusques. Bulletin de la Societe botanique de France. Bd. XXXVI. 



1880. 



