106 BOTANICAL RESULTS OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 



with the principal wings parallel to the substratum, as shown in fig. 7 (also PI. II., 

 phot. 4) ; in this case, as the figure indicates, the two ends of the cell appear completely 

 rounded. But not uncommonly individuals are to be found, in which wings 3, 6, or 

 4, 5 are parallel to the substratum (cf. fig. 10), and in such cases there is a prominent 

 papillose protrusion at each end of the cell, due to the fact that the principal wings 

 project further at these ends than do the lateral wings ; a glauce at figs. 7 and 9 

 should make this quite clear. The wings themselves are solid extensions of the 

 wall, into which the cell -cavity does not penetrate (cf. fig. 11); they are conical in 

 section, being broadest where they arise from the main body of the cell, and gradually 

 narrowing down to a rounded edge (fig. 11). In the side-views of the cell a very faint 

 stratification of the solid wings could occasionally be observed, especially in stained 

 preparations. At the middle of its longitudinal course each wing is provided with a 

 slight but perfectly distinct notch (PI. L, figs. 7, 10, 12 ; PL II., phot. 4), which divides 

 into two symmetrical halves ; this is an absolutely constant feature. The wings are 

 quite rigid and stand off stiffly at right angles to the surface of the cell ; in a drop 

 of water the cells can be made to roll over and over without any apparent bending 

 of the wings taking place. 



The cell-contents of S. antarctica were very difficult to decipher. It has been 

 impossible to make out any details as to the shape of the chloroplast, which, however, 

 appears to be single. Staining with iodine or haematoxylin sometimes brings out a 

 small round body (figs. 11 and 13), which . may be either a nucleus or pyrenoid, 

 probably the latter. As a general rule, very little or no starch was demonstrable in the 

 cell-contents, although occasional cells contained quite a lot. The abundant presence 

 of the yellowish-white fat in the contents makes them astonishingly similar to those 

 of ddorosphsera antarctica. As in the latter case, the distribution of the fat shows con- 

 siderable diversity. The contents mostly occupied the whole body of the cell, and in 

 such cases the granular protoplasm is found in the middle, and a cap of fat at each end 

 of the cell-cavity ; commonly these two caps of fat are roughly equal in size and more 

 or less concavo-convex in shape, the concave side having an irregular outline, and being 

 directed towards the granular protoplasm in the centre of the cell. In other individuals 

 two additional lumps of fat on either side of the cell occurred together with the other 

 two masses. In some individuals, finally, the whole of the protoplasm was obscured by 

 the fat, such cells presenting an opaque, yellowish-white, and homogeneous appearance. 



Owing to the very marked similarity of the cell-contents in Scotiella antarctica and 

 Chlorosphsera antarctica, I was at one time inclined to regard the large isolated cells of 

 the latter as resting-stages of the Scotiella. This view seemed to obtain additional 

 support from the fact that now and again an individual of S. antarctica is to be found in 

 which the contents appear rounded off (PI. I., fig. 16), and look very similar to a large 

 Chlorosphasra-cell (except for the absence of the mucilage-envelope). There is, however, 

 a good deal that speaks against such an assumption. In the first place, it would appear 

 as though the Scotiella forms resting-cells of a rather different type (cf. fig. 15 and the 



