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is now stated to have been wrongly figured in Ralfs. And, thirdly, I was unwilling, unless fortified by more evidence, to multiply species and varieties or to introduce confusion, if I could help it.

Mr. Archer's doubts as to some of my identifications are therefore, I confess, not unwarranted, and it is quite possible that future observers, noting the peculiarities of our New Zealand Desmids, minute as these peculiarities often are, may go beyond me and endeavour to raise the plants to distinct rank. Still, even now, when I have had the advantage of longer examination and extended means of reference, I hesitate to do so. In the cases of some plants, specially mentioned in Mr. Archer's paper, notes and explanations will be found in the following pages: as regards many of the others, want of time has prevented me from devoting to them so close an observation as would be necessary to elucidate such minute features. As will be seen below, I am almost tempted to boldly make a new species of the plant which, in my former paper, I referred to Micrasterias rotata; but even in that case I refrain from doing so.

Sphœrozosma excavatum, Ralfs.

I find that this plant is somewhat less rare than I thought it to be; but still I can by no means consider it common: and in consequence of its great fragility connected filaments are found much more seldom than separate joints.

Micrasterias rotata, Greville; and

Micrasterias denticulata, Brébisson.

With regard to the distinction between these two, I find from Mr. Archer's paper that that there is no doubt about it, owing to the difference between the zygospores. These I have never yet seen, and my only means of distinguishing were the teeth of the lateral lobes; and as both sharp and truncate teeth are found here indiscriminately, sometimes all round the frond, sometimes sharp on one segment and truncate on the other, sometimes both sharp and truncate on the same segment, I am still greatly in doubt whether M. denticulata occurs here at all.

And now as to our M. rotata. Is it identical with the English plant, or so nearly so as to be considered the same, or shall it be erected into a new species? Here my doubts arise from the second of the sources mentioned just now; that is, an uncertainty whether some of the features noticeable here may not occur in European plants but have been either overlooked by authors or mentioned somewhere unknown to me.

The first difference is size. According to Ralfs the dimensions of M. rotata are,—length, ¹⁄₉₁ inch; breadth, ¹⁄₁₀₄ inch: and Rabenhorst's measurements apparently agree with this. Reduced to modern nomen-