222 BRITISH DESMIUIE.K. 



Closterium gracile differs from the other rostrate species in its smooth 

 frond. Its beaks are shorter than those of C. rostratum and C. setaceum, 

 and its frond is less inflated. 



36. C. tenerrimum (Kiitz.). 



Closterium tenerrimum, Kiitzing, Phycologia Germanica, p. 130 (1845) ; in 

 lit. cum icone. 



Nordhausen, Kiitzing. 



I can perceive in Professor Kiitzing' s drawing no character by which this 

 plant can be separated from Closterium, acutum. 



Tab. XXXV. fig. 10. Fronds : from a drawing by Professor Kiitzing. 



ANKISTRODESMUS, Corda. 



2. A. fusiformis (Corda). 



Anhistrodesmus fusiformis, Corda, Almanack de Caidsbad 1838, p. 199. t. 2. 

 f. 18. 



Carlsbad, Corda. 



3. A. convolutus (Corda). 



Ankistrodesmus convolutus, Corda, Almanack de Carlsbad 1838, p. 199. t. 2. 

 f. 19. 



Carlsbad, Corda. 



I am unacquainted with the characters of these species. 



SCENEDESMUS, Meyen. 



7. S. antennatus (Breb.) ; cells fusiform, somewhat ventricose at the 

 middle ; ends cuspidate, each terminated by a minute orbicular 

 globule. 



Seenedesmtis antennatus, Brebisson, in lit. cum icone (1846). 

 Falaise, Brebisson. 



Scenedestnus anfen?iatus resembles S. obliquiis in form, and also in the 

 arrangement of its cells ; but it is distinguished from that and every other 

 species by having the attenuated points tipped by min\ite globules. 



Tab. XXXV. fig. 27. a, b. different states of frond : from drawings by 

 M. de BreTsisson. 



