Maskell. — On New Zealand Desmidieae. SOS 



Very rare, I think. At least I have only seen two specimens in as many 

 years. It is excessively fragile. 



S.JUforme, Ehrenberg. (E. p. 209.) 



Fig. 25. 



Distinguished from the other species of the genus by having the joints 

 united by double processes inclosing a quadrate foramen, instead of only a 

 single process. 



Bare, but perhaps more frequent than either of the two last. 



This plant appears not to exist in England, being referred by Ealfs only 

 to Germany. In specimens which I have preserved in fluid, the joints 

 sometimes seem to diminish and increase in size owing to the twisting of 

 the filament. The same appearance is seen in the American species, S. 

 pulchrum, Bailey, (Ealfs, p. 209). 



4. Micrasterias Agardh. 



M. rotata, Greville. (E. VIII.) 



Fig. 5. 



Common, especially in spring. 



M. denticidata, Brebisson. (E. VII.) 



Doubtful. 



There is great difficulty in satisfactorily distinguishing these two species, 

 and authorities are by no means clear. Ealfs doubts whether the two 

 plants are not really the same ; as also does Dr. Wallich in his description 

 of DesmidietB from Bengal ; and Mr. Archer* shows, that often in papers 

 M. denticulata has been referred to while M. rotata is meant. Mr. Archer, 

 indeed, strongly supports the distinction between the two. I would by no 

 means venture to intrude here in the discussion, beyond observing that 

 almost every specimen which I have seen has the eight subdivisions and 

 the sharp ultimate teeth of M. rotata ; secondly, that on a few occasions 

 I have found some which could doubtfully be referred to M. denticulata; 

 thirdly, that I was able once to observe the actual process of division 

 described and figured by Mr. Lobb,f and certainly the old segments of 

 the frond were M. rotata, though Mr. Lobb throughout refers to M. den- 

 ticulata. The process is shown in fig. 5 ; this, taken from a specimen 

 actually observed dividing, shows clearly the teeth of M. rotata; but 

 the new segments forming agree exactly with Mr. Lobb's figm'e. There 

 could be no doubt about it, the whole appearance of the plant was that 

 of M. rotata ; was there a confusion in Mr. Lobb's mind between the two ? 

 On the whole, I believe that M. rotata occurs here in profusion ; M, den- 

 ticulata perhaps also, but sparingly. 



* " Quart. Journ. of Micros. Science," n. series, vol. II., 1862, p. 244. 

 t " Trans. Micr. Soc. London," n. ser., vol. I., 1861, p. 1, and pi. I. 



