

102 BOTANICAL RESULTS OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 



determined, 18 species of algse and 2 fungi are concerned in the production of this 

 association. The algae observed are the following : 



Protoderma brownii, n. sp. (p. 102). Raphidonema nivale, Lagerh. (p. 116). 



Chlorosphaera antarctica, n. sp. (p. 103). Rapliidiuin pyrenogerum, Chod. 1 ? (p. 117). 



Scotiella antarctica, n. gen. et sp. (p. 105). Ulothrix subtilis, Kiitz. 



polyptera, n. sp. (p. 108). CEdogonium, sp. 



Pteromonas nivalis, Chod. (p. 109). Pleurococcus vulgaris, Menegh. 



Chodatella brevispina, n. sp. (p. 111). Chlamydomonas caudata, Wille. 

 Oocystis lacustris, Chod. f. nivalis, n. f. (p. 112). ,, sp. (p. 118). 



Sph&rocystis schroeteri, Chod. f. nivalis n. f. (p. 113). Mesoteenium endlicherianum, Naeg. 



Trochiscia antarctica, n. sp. (p. 116). Nostoc minutissimum, Kiitz. 



A considerable number of these forms will be considered in detail in the following 

 paragraphs. 



(a) PKOTODERMA BROWNII, n. sp. (PI. I., fig. 1 ; PI. II., phots. 1, 2, 3, 5, P). 



The main ground-mass is constituted by a form, which I somewhat doubtfully 

 refer to the genus Protoderma as a new species, P. brownii, n. sp. (PL I., fig. 1). 

 This alga probably forms broad sheets of cells, with an irregular margin spread out on 

 the surface of the snow, and may possibly serve as a basis for the growth of some of the 

 other forms (cf. p. 100). A rough examination discloses merely a number of more or less 

 rounded green protoplasmic masses, regularly arranged with reference to one another, 

 and separated by marked colourless intervals. The latter are due to the cell-walls, 

 which are markedly gelatinous ; a careful examination (especially of material stained 

 with gentian violet or methylene blue) reveals the polygonal (sometimes rather 

 rounded) network due to the middle lamellae of the walls and the (occasionally stratified) 

 mucilage, which intervenes between middle lamella and cell-contents. The middle 

 lamellae frequently exhibit a granular character. Where the cell-contents are not 

 obscured by the above-mentioned fat (which was frequently quite wanting in the cells 

 of the Protoderma, cf. p. 101), it is possible to make out a single chloroplast, which 

 generally takes the form of a curved plate, and may frequently be almost hemispherical. 

 In preparations stained with gentian violet a single pyreuoid was often to be distin- 

 guished in the chloroplast, while iodine generally showed the presence of a limited 

 number of starch-grains in the cells. In rare cases adjoining cells of relatively small 

 size were separated by thin and delicate walls ; such cells are no doubt daughter-cells 

 produced by division, prior to preservation of the material. These young daughter- 

 cells nearly always contained fat. On the whole, however, the Protoderma seemed in 

 as inactive a condition as the other constituents of this snow flora. The cells vary con- 

 siderably in size, from 5-12 M or even more, but small cells are the rule ; in most places 

 they form but a single layer, but, where extensive patches of the Protoderma were 

 observed, they appeared to lie in two (or more ? ) layers above one another. 



The remaining species of the genus Protoderma are characterised, according to recent 



