ALGOLOGICAL NOTES 



325 



fig. 1, E-H). I know of no other species of CEdogonium with a 

 holdfast quite of this nature. 



It will be noticed that both androzoogonidia and gynozoogo- 

 nidia arise in the large filaments which ultimately develop the 

 oogonia, and it may be inferred from the material that the two 

 types of zoogonidia arise at different periods. There would be 

 obviously no necessity for the formation of gynozoogonidia at 

 the time when the filaments contained oospheres ready for 

 fertilization. 



XI. — Eesting-spores of Surirella spiralis Kiitz. 



In a small boggy area in one part of Sutton Park, Warwick- 

 shire, Stirirella spiralis occurs in a living vegetative state all the 

 year round. The Algae of this bog have 

 been kept under continuous monthly ob- 

 servation for a period of over five years, 

 and, with one exception, only living cells 

 and empty valves of Surirella sjnralis 

 have been observed. On January 29th, 

 1908, one specimen was observed which 

 contained eight spores of approximately 

 equal size, obviously formed by the divi- 

 sion of the original protoplast into eight 

 parts (fig. 2). The contents of each spore 

 were oily, very refractive, and of a rich 

 brown colour. In outward shape the 

 spores were rounded-polygonal, and a 

 minute apiculus was present near one or 

 two of the blunt angles of each spore. 

 They were from 20 to 31 /x in diameter. 



The spore-walls were strong and thick, 

 having an appearance almost exactly like 

 the edges of the valves, from which one 

 might infer that they were to some extent 



silicified. t-- o c ■ 77 • 7- 



mi . , n T J- 1 1 Fig- 2. — Surirella sjnrahs, 



Ihick-walled restmg-spores have been ^ 459. single cell with 



seen in very few freshwater species, and eight thick-walled resting- 



only in a few genera of marine plankton spores. The detailed struc- 



Diatoms, but in none of these cases have ^''\^. °/ /^^^^ ^^^^^ '^ ^^^^ 



• 1 ■ 1 , 1 -ii • i.1 indicated, 



eight spores been observed withm the 



walls of the original mother-cell. It is 



in this respect that the spores of Surirella spiralis somewhat 



resemble the gonidia observed by Murray '■' in Coscinodiscus con- 



cinnus and ChcBtoceras borealis, although in these two marine 



plankton Diatoms the gonidia were not furnished with thick walls, 



and were not resting- spores. 



A comparison might also be made between the spores of 



Surirella spiralis and the small spores (microspores '?) described 



* G. Murray, " On the Reproduction of some Marine Diatoms," Proc. Roy. 

 Soc. Edinburgh, xxi. 1897. 



