ARCHER, ON A NEW SPECIES OF COSMARIUM. 251 



pressed near the ends, owing to the upward inclination of the 

 apices ; endochromc bright green, reaching near the ends, 

 and having beyond it, close to the apices, the active granules 

 — large granules in a single series, longitudinal fillets several; 

 empty frond frequently slightly reddish, especially near the 

 ends — longitudinal striae very fine and very numerous, in 

 mounted specimens very difficult of detection, but in recent 

 very readily made out. Sporangium large, orbicular, or very 

 broadly elliptic, smooth, placed between the empty fronds, 

 which arc for some time persistent. Conjugation taking 

 place soon after self- division, one, the younger segment of 

 each conjugating frond, is much shorter than the other, the 

 older, longer segment, each of which lies in a parallel po- 

 sition, pointing in the same direction. 



It is with much gratification that 1 take the opportunity to 

 name this species after a well-known microscopist, Andrew 

 Pritchard, Esq., author of several valuable additions to mi- 

 croscopical literature. When, at my request, Mr. Pritchard 

 did me the honour to permit me to dedicate this species to 

 him, he quaintly added that his only objection was that he 

 thought his name too long. I do not assent to this ; but, 

 even if it were, I might reply, that his services in the cause of 

 microscopy have indeed been long, and far more than deserv- 

 ing of this inadequate compliment. 



Measurements. — Length of frond, -^- to -^ ; breadth, ^^ 

 to ^;4-^ ; diameter of sporangium, ^4-^^ of an inch. 



Plate XII, fig. 25, frond with endochrome ; fig. 26, 

 empty frond ; fig. 27, conjugating fronds with sporangium. 

 All magnified 200 diameters. 



Affinities and dijferences. — To me it seems that there are 

 only four species with which there is any likelihood of this 

 Closterium being confounded, and those are — Closterium 

 turgidum, Elir., C. attenuatum, Ehr. (opposed as may seepi 

 the specific names of those species), C. acerosum, Ehr., 

 and C. lanceolatum, Kg. Closterium Pritchardianum agrees 

 with C. turgidum in its gently curved but slightly tapering 

 frond, in its lower margin being curved upwards towards the 

 reddish apices, in its endochrome possessing longitudinal 

 fillets and a single series of large granules, and in its empty 

 frond being finely striate ; but the former differs from the 

 latter in its less stout and less curved frond, in its conical 

 and truncate, not broadly rounded, ends, and in the striae 

 seen on the empty frond being far more fine and close. C. 

 Pritchardianum agrees Avith C. attenuatimi in the size and 

 general curvature of the frond ; but the former differs from 

 the latter in its conically tapered, truncate ends, not suddenly 



