Maskell. — On the New Zealand Desnridieas. 249 



is now stated to have been wrongly figured in Ealfs. 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. 



SpJuerozosma excavatum, Ealfs. 



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, Brebisson. 



Fig. 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 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, 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 Ealfs the dimensions of 

 M. rotata are, — length, -J- T inch ; breadth, - ± ^ inch : and Eabenhorst's 

 measurements apparently agree with this. Eeduced to modern nomen- 



