Maskell. — On the New Zealand Desmidiese. 251 



I have already mentioned that this plant, which was common here two 

 years ago, has heen very scarce of late : and no sign of conjugation has as 

 yet come under my observation. 



Holocystis incisa. 



Mr. Archer unites this to Micrasterias (other authors, I find, include it 

 under Tetrachastrum) ; and he states, that instead of being identical, as I had 

 thought, with Dr. Wallich's Indian plant, it is probably the same as a plant 

 from Sweden, reported by Cleve and called M. decemdentata /3 upsaliensis. 



Euastrum binale, Turpin. 



The plant mentioned by me (vol. xiii., p. 306) as either this or E. elegans 

 is certainly E. binale, as I have satisfied myself by comparison with Ralfs' 

 figures, and with specimens in my English gatherings. E. elegans shows 

 the sides of the terminal notch extending considerably beyond the lateral 

 spines. I regret to say that the figure 26 in vol. xiii., pi. xii., is about as 

 unlike the plant which it is supposed to represent as it is possible to be ; 

 and unluckily Mr. Archer has been misled by it to take my Euastrum for a 

 new thing. My original drawing was meant to be, and I think was, almost 

 exactly resembling Ralfs' figure 8 d (or 8/) in his pi. xiv. 



Cosmarium margaritiferum . 



I believe that several of the forms supposed by me to belong to this 

 species were really C. tetraophthalmum, C. broomeii, etc., or at least closely 

 allied to them. C. biretum I have never seen here : C. botrytis is certainly 

 common. The conjugation of C. margaritiferum I saw once, and could detect 

 no difference from the European plant. In this case also the printed figures 

 in pi. xii., vol. xiii., figs. 27, 28, and 29, are unsatisfactory. Fig. 28 was 

 intended to show a slight truncation, but it does not show any. 



Cosmarium crenatum, Ralfs. 



Fig. 15. 



If Ralfs' figure 7, pi. xv M be correct, our New Zealand form differs 

 from the English one by having its ends (as my figure shows) straight, 

 without crenations. I think also that the segments are somewhat wider at 

 the base. Length of frond 30-5 fj. ; breadth 27 /x. 



Cosmarium botrytis, Bory. 



In examining this plant I have been able to detect a very decided volun- 

 tary motion, which on one occasion I observed for nearly three hours. As 

 far as I can gather from works available to me, it has never been satisfac- 

 torily shown that the Desmidiea? travel voluntarily, that is, in the manner 

 in which Diatoms travel. It has long been known that Desmids " move ;" 

 that is, they will come to the surface if buried in mud, or to the side of a 

 vessel nearest to the light. But such movements as these, as Ralfs remarks 

 (p. 22), may be due rather to the stimulus of light than to " voluntary 



