MASKELL.— On the New Zealand Desmidiex. 949 
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. 
Spharozosma 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 sepa- 
rate joints. 
Micrasterias rotata, Greville; and 
Micrasterias denticulata, Brébisson. 
ig. 16. 
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 haye 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, some- 
times 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, jg, inch; breadth, 4$z inch: and Rabenhorst's 
measurements apparently agree with this. Reduced to modern nomen- 
