338 FRESHWATER ALGE COLLECTED IN THE SOUTIL ORKNEY. 
Fritsch; U= Ulothrir. Photographs 1, 2, and 3 are magnified 130 times ; photographs 4, 
5, and 6 are magnified 400 times.) 
Photographs 1 and 2.—Typical views of the yellow snow flora at a low magnification. Tn 
the first photograph Protederma antarctica is very predominant, but in the 
centre is seen a group of fairly large Chlorosphera-cells, together with three 
individuals of Scoticlle antarctica. Short filaments of Ulothrix ave visible at 
several points in the photograph. The second photograph shows a very typical 
stratum of Protoderma near the centre, two young colonies of Spherocystis at 
the upper end and an older colony towards the base,  Chlurosphera-cells of 
various sizes and often exhibiting well-marked mucilaye-sheaths are obvious at 
many points in the photograph, 
Photograph 3.--This shows a very typical group of large Chlorosphera-cells with well- 
marked sheaths together with a thick patch of Protoderma., At the right-hand 
side of the photograph a number of oval individuals of Chodatella are to be seen, 
Photograph 4.—Ап individual of Scotielia antarctica, Г. X. Fritsch, showing the two 
© principal and two lateral wings. The notch in the right-hand principal wing is 
very obvious, At the lower end of the individual the two lateral wings can be 
seen curving inwards, 
Photograph 5.--А small part of a Profoderma-sheet highly magnified (only the cell-contents 
are recognisable) and showing a number of individuals of Chodatella brevispina, 
F. E. Fritsch. Тһе small spines on the latter are scarcely visible, 
Photograph 6.—This shows part of the central group of cells in photograph 1 on an enlarged 
scale. ‘Three individuals of Scotiella, a number of Chlorosphera-cells and 
Ulothriv-filaments are visible, while the ground-mass consists of Protoderma. 
