114 DUBLIN XTNTVEESITY 



of course, the fusiform species. To some it may, perhaps, seem prema- 

 ture to found a genus upon the characters presented by the mature form 

 alone, without acquaintance with the reproductive state. But it will be 

 recollected that none of the genera, according to Ralfs, are founded upon 

 any appearance or phenomenon presented by the mode of conjugation, 

 or form of the sporangium, and it is rarely employed as a specific cha- 

 racter; and this, for necessary and obvious reasons: the sporangia of 

 numerous species are not known, in many but rarely met with, while 

 in the same genus considerable diversity sometimes occurs in the sporan- 

 gium, such as the form of the spines and other particulars. For my own 

 Bhare, I do not see any course open but to make a new genus. From 

 the simplicity of form, however, I have found some difficulty in draw- 

 ing up concise characters : I trust, however, the following may be found 

 to meet the requirements of the case : — 



Class.— ALG.^. 



Order. — Chloeospoee^j or Confervoideje. 



Family. — Desmidiace^. 



Leptocystinema (nov. gen.). 



Plant an elongated jointed filament (often separating); joints straight, 

 much elongated and slender, without a central constriction or inflation, 

 entire, ends simply truncate, or dilated and truncate (no evident gela- 

 tinous sheath). 



1. — Leptocystinema Kinahani (nov. sp.). 



Filaments attached, frequently breaking up into separate joints, 

 which are slender, extremely elongate, linear, cylindrical, and smooth, 

 their ends abruptly truncate ; the junction of the halves marked by a 

 pale transverse interruption of the cell-contents ; endochrome forming 

 a compressed longitudinal band, its broader diameter extending the 

 entire width of the joint, — the narrower not filling more than one-third, 

 and presenting an undulating outline, — at the extremities of the joint 

 more or less retracted from the end of the primordial utricle, leaving a 

 clear space, in which are active granules ; the endochrome also having 

 immersed within it a single longitudinal central series of light-coloured, 

 well-defined, globular, dense corpuscles, one of these bodies occupying 

 the centre of the transverse pale space. 



