218 MONOCYSTE^E. 



fronds may be easily distinguished with the naked eye in 

 spite of their smallness, their green colour trenching upon the 

 discoloured parts of the plants upon which they are fixed. 

 At first sight one might be induced to believe that they are 

 but parts of those plants whose chromule has not been dis- 

 organised by the immersion which has discoloured their other 

 parts. These rosettes follow the forms of their supports. I 

 have seen them upon Conferva fracta ; they then embrace the 

 filaments in such a manner as to surround them with a sort 

 of ferrule or annular hood. A slight magnifying power of 

 the microscope is sufficient to show the elegant disposition of 

 radiating filaments which, by their approximation and lateral 

 union, resemble an areolated disc, which recalls to mind cer- 

 tain Pediastra belonging to the Desmidece. 



"The fronds are roundish, from one to two, rarely three mil- 

 lemetres in diameter ; they are formed of filaments closely ap- 

 plied to the plant on which they grow, dichotomously branched ; 

 branches approximate, and as though soldered the one to the 

 other. The articulations or cells three or four times as long 

 as broad, often unequal, are furnished interiorly with a green 

 granular endochrome. On a great number of these articula- 

 tions is remarked a tubercular rounded projection or pro- 

 tuberance, from which arises a tubular filament, truncated a 

 little, dilated at the summit, from the interior of which issues 

 a long and very delicate thread. This part of the organiza- 

 tion of this Alga show T s clearly that it ought to be placed in 

 the Chcetophoroidece, and near to Bulboch&te. This setifer- 

 ous sheath is very caducous and difficult to perceive. 



" At a certain period of the existence of Coleochcste scutata 

 its disc is covered here and there with tuberculated masses of 

 endochrome, which one might regard as the formation of 

 spores, at a later period indeed, these little masses are con- 

 verted into groups of globules charged with the tube or seti- 

 ferous sheath which characterizes this Alga. In the first 

 period of its developement, the tubes terminate in a point, 

 from whence issues a long setaceous filament of great te- 

 nuity ; at a later period, the summit of this sheath is open, 

 and appears then truncated and slightly dilated. 



