Page:Transactions NZ Institute Volume 15.djvu/322

tetraophthalmum, Closterium acerosum, Clost. lineatum, 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 Algæ 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., Desmidium, 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 endeavouring to bring into general use. Instead of the old "inch," and fractions of it, which were only intelligible to Englishmen, micro-measurements are now expressed by the symbol μ, representing a micro-millimetre. One μ = ¹⁄₁₀₀₀ millimetre = ¹⁄₂₅₀₀₀ inch almost: so that, for example, instead of saying that Micrasterias rotata has a length of ¹⁄₉₀ inch, one would say nowadays 278 μ. This mode is intelligible to observers of all countries, 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 Desmids, 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.

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

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

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

I have not seen this plant, which Dr. Spencer informs me occurs very rarely in Hawke's Bay.