Maskell. — On New Zealand Desmidiete. 301 



not seem to have been mentioned by authors. The discussion of these would 

 lead me bej^ond the scope of this paper, and perhaps the characters to 

 which I refer would not even suffice to raise the plants even to " varieties." 



It will be seen fi-om my list that the following genera are not, as far as I 

 know, represented here (I sx^eak of the neighbourhood of Christchurch) : — 

 Didymoprium, Desmidium, Xanthidium, Arthrodesmus, Tetmemorus. Also, that 

 Evastrum and Cosmarium appear to furnish comparatively few species, and 

 Staurastnim, out of fifty-six species described, has furnished only seven, 



I have not mentioned, as a rule, the locality of each species observed, 

 desu'ing rather to avoid iteration. In two or three cases where I have ob- 

 tained specimens from other places, the fact is stated ; but, where no men- 

 tion is made, the plant was gathered in the neighbourhood of Christchurch, 

 and chiefly in the fish-ponds of acclimatization societies. 



I may remark, in conclusion, that I have preserved in slides almost all 

 the plants named in the following catalogue. In the process of preservation 

 the question of the best fluid for the purpose naturally engaged much atten- 

 tion, and I have tried several. No fluid, as my experience goes, is enthely 

 satisfactory. Camphor- water and Thwaites' fluid appear at first to preserve 

 the plants in all their natural beauty and colom', but after a time they fail. 

 Ealfs' fluid has the same objection, and is, moreover, not very clean. 

 Glycerine, to which I have had final recourse, is the best of all. When the 

 plants are first immersed in it they usually, indeed, shrivel into shapeless 

 masses, but after a few minutes they swell out again and regain their proper 

 form. In glycerine, as in all the other fluids, the endochrome is much 

 affected, but I think that the beauty of the cell-walls themselves is brought 

 out better in this than anything else. Spirotcenia will not stand anything, 

 even distilled water spoils it. As a matter of fact, no Desmid can really be 

 preserved unhurt, and no preserved specimen can equal the natural plant. 

 In the Diatomaceae the case is quite different. But, taking them all round, 

 I believe that of all preservative fluids glycerine is the best. 



CATALOGUE OF DESMIDIE^. 



1, Hyalotheca, Ehrenberg. 

 H. dissiliens, Smith. (E. I.)* 

 Common, especially in spring. 



This plant seems particularly liable to a disease (?) produced apparently 

 by a species of Pythium. 



* The letter K with a figure after the name of a species denotes the plate in 

 Ealfs' work where the plant is figured. Thus (R. XVI.) means, "Ealfs' 'British Desmi- 

 dieffi,' Plate XVI." 



