260 AKCHER, ON A NEW SPECIES OF ANKISTRODESMUS. 



save mere self-division in the manner deseribedj the position 

 of the genus is^ therefore^ doubtful. 



Probably, for the present, it is best to consider it as a 

 doubtful or aberrant genus of Desmidiacese. Its oblique self- 

 division, so far as it goes, is somewhat like that of Spirottenia, 

 but there is no fm'ther resemblance. Nageli"^ and E-abenhorstf 

 place Eaphidium (equivalent to Ankistrodesmus) amongst 

 Palmellacse ; but the very elongate, acute cells are very unlike 

 anything else in that family. De BaryJ alludes to this genus 

 as doubtfully Desmidian. 



Assuming that I have proved ray plant to be a true Ankis- 

 trodesmus, and not a Closterium, it may be well to compare 

 it with the other admitted species of that genus. It agrees 

 with A. falcatus in its very slender and acute cells, but it 

 diflFers from it by its straight, not arcuate, cells, by its fusiform, 

 more quickly attenuated, cells, by its more intensely acute 

 extremities, and by the constituent cells of an old fasciculus 

 being much fewer in number. It is, indeed, a very ditierent 

 plant. This form scarcely agrees at all, except generieally 

 (as I think), with A. convolutus, Corda, the cells differing, as 

 they do, in their very slender (not, comparatively, stout) form, 

 in their straight (not crescent-shaped) outline, and in their 

 extremely acute extremities. With A. contortus, Thuret, this 

 form agrees in the very acute cells, but it differs in their 

 straight (not arcuate or sigmoid) form, and in the cells being 

 not inflated at the middle. 



I have in the foregoing remarks alluded to the distinctive 

 characters of Closterium and Ankistrodesmus as regards the 

 mode of self-division. I conceive it may be quite worth while, 

 in connexion therewith, to draw attention to a remarkable 

 state of Closterium acutum, Breb., (it may be C. subulatum., 

 Breb., but I am disposed to think these are synonymous). 

 This consists of a curious aggregation of fronds of that 

 Closterium into chains and bundles in the manner I represent 

 in the accompanying sketch of some of the most remarkable 

 of these cases (figs. 58 to 60, x 200). The fronds were some- 

 times juxtaposed side by side, sometimes irregularly, at other 

 times combined into a kind of chain, while multitudes of 

 fronds, in the ordinary free condition, abounded in the 

 gathering. This, whatever it portend, was no accidental 

 juxtaposition ; for they, not unfrequently, in order to accom- 

 modate themselves to one another in the combination, were 

 of a sigmoid or otherwise curved and bent character, yet no 



* Op. cit. 



f 'Algen Sachs.' 



X ' Untersucbuiigen ixber die Familie der Cotijugaten/ p. 77. 



