256 Rev. M. J. Berkeley on a new species of Closterium. 



plates being probably suppressed ; finally, that the basal or 

 stem-bearing plate is the homologue of the madreporiform body. 



It was our intention to have added some illustrations to the 

 present memoir, but on consideration we think it better to run 

 no risk of misrepresenting Prof. Miiller. 



XXIII. — Description of a new species 0/ Closterium {Closterium 

 Griffithii). By the Rev. M. J. Berkeley, M.A., F.L.S. 



[With a Plate.] 



A PRETTY but rather puzzling little Alga has been nursed for 

 two years or more by Dr. J. W. Griffith in bog water, in which 

 it has multiplied, without however giving any opportunity of 

 ascertaining its mode of propagation. I have lately had occa- 

 sion to examine mounted specimens, accompanied by a mag- 

 nified representation of the plant in a living state, and from 

 these and notes communicated by Dr. Griffith, who is preparing 

 a work on the microscope, to the appearance of which I am 

 looking forward with much interest, it is quite clear that it belongs 

 to the genus Closterium^ notwithstanding its comparatively minute 

 size, the absence of curvature, and the hitherto unobserved copu- 

 lation of the filaments. The circulation, which can only be seen 

 under a power of from 1000 to 1500 diameters, is precisely that 

 of Closterium, and the green colour and absence of lateral mark- 

 ing forbid the notion of its being a Synedra, though there are 

 one or two species figured by Kiitzing to which it has some 

 resemblance in point of form. The species may be characterized 

 as follows : — . 



Closterium Griffithii. Minutum rectum fusiforme medio turgi- 

 dulum, utrinque fortiter attenuatum apicibus acutissimis setaceis 

 hyalinis. Long. •033--025 unc, centro lat. •0002--0016. 



At first the frond is green, but a hyaline band is at length 

 formed in the centre, where division ultimately takes place. 

 Closterium setaceum resembles it somewhat in form, but that is 

 more swollen in the centre, much longer, striated, and the tips 

 of the fronds are curved. The var. /3. of C. cornu approaches it 

 in size, but the whole outline is extremely diff'erent. There cau 

 be no doubt of its being a very distinct species. The figure 

 (PI. XIV. fig. 2) represents three individuals in diff'erent stages 

 of growth magnified 450 diameters. The species belongs to 

 the genus Stauroceras, Kiitz., which is very properly considered 

 as part of Closterium by Mr. Ralfs. 



