f; e. fritsch. 



South Orkneys {op. ciL, p. 330). There is undoubtedly some variation in the 

 degree of separation of the cells in P. crispa, although it does not appear ever 

 to attain to the pronounced separation typical of P. antarctica. Since seeing the 

 typical form of the latter species in the present material, I have realised that 

 it was not present in the South Orkneys material at all. 



The most pronounced diflference between P. antartica and P. crispa lies in the 

 thickness of the walls separating adjacent cells. In P. antarctica their thickness 

 is generally nearly equal to the width of the cell-contents, so that the latter 



88B SSSSBSSooSS 



OOOaaaoon RS^Onnn 



DO no 00 DO DD DO DO 

 00 DD Da DO OD DO DQ 

 00 OD g DD °° DO no 



no DO DO on dd oa no 

 □ Da, 

 <=" on 





wmm^ 





J 



:& 



aooDo 

 ooooo 

 □oooo 



OQQOQ 



goqoo 



qOooq 



OOOOq 



OOOOa 



lOOOOo 

 \ OOooo 



\ aOO O 

 \ OO o 



0000 





A-D. Prasiola crispa (Lightf.) Menegh. ; A, part of thallua showing formation o( akinetes (ft) ; B, a normal piece of the thallus ; C and D, 

 stages in the germination of akinetes ; E, F, Prasiola antarctica Kiitz. ; E, normal piece of the thallus ; F, edge of thallus^ showing 

 commencing formation of packets ; G-J, Prasiola calophylla Kiitz. ; G, two plants ; H, small part of stalk ; I, broadening out of stalk into 

 lamina ; J, edge of broad part of lamina. (G, magnified about 6 times ; C and D, X 700 ; all other flgs., X 600.) 



appear remote from one another (text-figure E). The arrangement of the cells in 

 groups separated by wide interspaces is thereby rendered far less distinct, and in 

 parts of the thalli from Mt. Terror was quite unrecognisable. As a consequence 

 the thalli present an even more uniform appearance under the microscope than 

 obtains in P. crispa. In the material from Mt. Terror there also appeared to be 

 a tendency for the cells to be squarer in surface-view than is usually the case in 

 P. crispa. The margins of the thalli were not as irregular as in the latter species, 

 • and the size of the whole plant was appreciably less ; some of the thalli in my 



