COLLECTED IN THE SOUTH ORKNEYS. 317 
and 7. reticularis *, but both these species have larger cells, and there are 
differences in the character of the membrane. The yellow snow form may 
provisionally be regarded as a distinct species, T. antarctica, characterized by 
the peculiarly shaped processes on the membrane, the thick walls, and the 
faculty of fat-storage tf. Attention may, however, be drawn to the similarity 
between this form and the zygospores of two species of Chlamydomonas, 
viz. C. nivalist and C. globulosa $ ; especially in the latter case there is 
some considerable resemblance. The character of the contents of Trochiscia 
antarctica was, however, not at all like that of a zygospore, since as a general 
rule no great quantity of food-reserves were present, and nothing to indicate 
any relation to a species of Chlamydomonas was observed in the material. 
In fact, 7. antarctica presents more the appearance of an independent Alga 
than many other species of the genus do. 
(j) RAPHIDONEMA NIVALE, Lagerh. (РІ. 10. figs. 32, 33.) 
A not uncommon member of the yellow snow flora consists of short filaments 
of three or four (but occasionally many) cells running to a point at one or 
both ends (Pl. 10. figs. 32, 33). The cells are provided with a very thin 
membrane and contain but a single chloroplast without a pyrenoid. The 
filaments were generally more or less curved (fig. 33), and when only one 
end was pointed the other was rounded off (fig. 32). These filaments are 
undoubtedly referable to Lagerheim's genus Raphidonema |. He observed 
vegetative reproduetion of this form, the threads breaking into two halves, 
each of which has at first one pointed and one rounded end. The stage 
shown in my fig. 32 undoubtedly shows one of the products of such a 
division. Subsequently, according to Lagerheim, the round end grows into 
anew hair-like point. Most of the individuals found in the yellow snow 
were of narrower dimensions than Lagerheim’s form, and the cells were 
rather longer (fig. 33) ; but filaments were found here and there quite 
agreeing with Raphidonema nivale, and there is no reason to regard the 
forms in the yellow snow as distinct from this species. 
In his recent revision of the green Algae, Wille includes Lagerheim's 
Raphidonema in the genus Raphidium, Kütz. (= Ankistrodesmus, Corda) ; 
* Hansgirg, * Prodromus d, Algenflora v. Böhmen,’ ii., 1892, рр. 240, 241. 
+ A full diagnosis of TrocAiseia antarctica will be found on p. 325. 
t Wille, “ Algol. Notizen, IX.-XIV.," in Nyt Mag. f. Naturvidenskab. xli. 1903, pl. 8. 
fig. 45. | 
$ Cf. Chodat, * Algues vertes de la Suisse,’ 1902, p. 182, fig. 60 D. 
| Lagerheim, “Schneeflora des Pichincha," in Ber. Deut. Bot. Ges. x. 1892, p. 523 
& pl. 28. figs. 15-21. 
* Wille, in Engler-Prantl, Die natürl. Pflanzenfam. Nachtr. ғ. Teil I. Abt. 2, 1909, 
р. 68. 
