128 BOTANICAL RESULTS OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 



by Svedelius from Patagonia, and by Wille from Cape Adare (" Antarktische Algen. 

 Mitteilungen iiber einige von C. E. Borchgrevink auf clem antarktischen Festlande gesam- 

 melte Pflanzen," Nyt Magazin f. Naturvidenskab, xl., 1902, pp. 209-219). Various 

 authors, who have dealt with the Antarctic Prasiolas, have held rather different views as 

 to the specific determinations ; several (such as Kiitzing, Rabeuhorst, and Svedelius) con- 

 sider that there are two species, Prasiola crispa and Prasiola antarctica, Kiitz. 1 These 

 different views are fully considered in the paper of Wille above cited. On the basis of 

 a careful investigation of Borchgrevink's material from Cape Adare, Wille (loc. cit., 

 p. 217) comes to the conclusion that there is no true point of difference between 

 P. antarctica and P. crispa ; it appears, however, that Borchgrevink's material was 

 the true P. cnspa and not the form described as P. antarctica by other authorities. 



There appears to be no doubt that some of the Antarctic Prasiola is distinguished 

 from the normal P. crispa by larger interspaces between the areolse and prominent 

 thickening of the outer walls of the cells, but it may be questioned whether they warrant 

 the establishment of a distinct species. The differences do not appear to be of specific 

 value, and the case would perhaps be best met by regarding the Antarctic type as a 

 var. antarctica of P. crispa. No typical specimens of P. antarctica were present in 

 the material from the South Orkneys. 2 



My material showed most of the stages figured by Wille on his pi. iii. Numerous 

 filaments of the Hormidium-stage were observed, but in many of them a considerable 

 number of the cells were dead or dying, and it appeared that the filaments were under- 

 going fragmentation without coming to anything further. Stages like those shown in 

 Wille's figs. 13 and 14 were also not uncommon. Little detached groups of cells, like 

 those of Wille's figs. 11 and 12 were very common in the sediment at the bottom of 

 the tubes. It appears that such groups of cells are not necessarily formed only in the 

 marginal portions of the thallus. In some specimens there were extensive strips of the 

 thallus in which the cells were obviously in a moribund condition, and in the centre of 

 such patches there was often a small rounded group of living cells with very abundant 

 contents. The surrounding dying cells were of considerably larger dimensions than the 

 others, and looked as though they had not divided recently. No doubt the central 

 group of living cells becomes freed by the dying away of the surrounding part of the 

 thallus, and acts as an organ of vegetative propagation. 



The cells of the South Orkneys material had a curious purplish or olive-brown tinge, 

 which is probably due to the action of the preservative (1 per cent, phenol) ; staining with 

 iodine brought out the chloroplast and pyrenoid very plainly. The dimensions were as 

 follows : width of cells = 4 n ; length = 6 /* ; thickness (i.e. dimensions at right angles to 

 surface of thallus) = 13 yu. There was always only a single layer of cells. 



1 Cf. also W. and Q. S. West, Brit. Antarct. Exped., 1907-09, vol. i., Biology, part vii., "Freshwater Algae," 1911, 

 p. 272-274. 



2 Since writing the report on the Algae of the South Orkneys, which was published in the Journ. Linn. Soc., I 

 have examined the true Prasiola antarctica, and this has consequently led me to modify slightly my remarks on the 

 two species given in the Linn. Soc. paper. 



