238 Transactions. — Botany. 



tetraophthalmum, Closterium acerosum, Clost. lincatum, Penium margaritaceum, 

 and a few more. Still, conjugation seems to be very rare here, and Dr. 

 Spencer tells me that it is equally so in Hawke's Bay. By the way, it is 

 curious how capricious the Algns often seem to be in their appearance and 

 disappearance. For example, two years ago, Micrasterias rotata and M. 

 ampullacea swarmed in some pools. This year both are exceedingly scarce 

 about Christchurch. Volvox globator was to be found, in 1878 and 1879, in 

 myriads: since then I have seen very few, and during the last twelve months 

 not a single specimen. 



It will be observed that, with the help of the Hawke's Bay gatherings, I 

 have been able to add three genera to the New Zealand Flora, viz., Desmi- 

 clium, Xanthidium, and Arthrodesmus ; but I have not found any of these in 

 Canterbury. 



The measurements adopted in this paper are expressed in the modern 

 nomenclature which, as I understand, microscopists in Europe are endea- 

 vouring to bring into general use. Instead of the old "inch," and 

 fractions of it, which were only intelligible to Englishmen, micro-measure- 

 ments are now expressed by the symbol fi, representing a micro -millimetre. 

 One /.i = xoVo millimetre = 251500 mcu almost : so that, for example, 

 instead of saying that Micrasterias rotata has a length of -^ inch, one would 

 say nowadays 278 /i. This mode is intelligible to observers of all coun- 

 tries, and is undoubtedly preferable to the old one. 



I regret to say that a little ditch near the Fendalton Road, which has 

 supplied me with some of the most curious of the New Zealand Desnrids, 

 including Triploceras tridentatum, Staurastrum aculeatum, and others, will 

 soon be no longer available. At the best it was only a little " grip" in a 

 field, almost dry in summer ; and it was always a puzzle to me how so 

 many uncommon forms got there, especially as it could not have existed 

 many years. But now the march of progress is rapidly effacing it, and the 

 streets of the flourishing village of Bryndwr will probably in a few weeks 

 destroy it altogether. The worst of it is that I know no other habitat in 

 Canterbury for some of these forms. 



Part I. 



Additions to Catalogue of New Zealand Desinidieas. 



1. Desmidium, Agardh. 



D. swartzii, Agardh. S. (R. IV.) 



Not uncommon, apparently, in Hawke's Bay. It has not been found in 

 Canterbury. 



D. aptogonium, Brcbisson. S. (R. XXXII.) 



I have not seen this plant, which Dr. Spencer informs me occurs very 

 rarely in Hawke's Bay, 



