CYSTOSPEKME^E. 187 



will be seen, is not in all respects inaccurate, though still, 

 for the most part, very erroneous : 



" When the Proliferce are ready to reproduce, cylindrical 

 enlargements are seen to arise in the length of the filaments, 

 which one would take for knots, if the plants were not arti- 

 culated or chambered. These bourrelets, at first but little 

 apparent, soon increase in size, and finally become covered 

 with a pulverulent material, which is formed either by refuse 

 matter which floats in the liquid, and which has been re- 

 tained within the elevations, or of a material which is secreted 

 by the Conferva. When this powder has remained some 

 time upon the enlarged part of the stem, a number of fila- 

 ments are seen to issue from it, which form at first little 

 rounded heads. Unfortunately this powder at the same 

 time that it seems to favour the increase of the young Con- 

 ferva baffles greatly the observer. He is able to see but 

 little of the first developement of the plant, and in conse- 

 quence is not able to judge, whether it issues from the sur- 

 face of the enlargement or from the centre : whichever it 

 may be, the young filaments extend themselves round all the 

 circumference, where they form as it were a tuft of hairs. 

 Little by little their cells begin to be marked out ; soon their 

 tubes resemble in miniature those of the great ProHferce. 

 Lastly, they go and form elsewhere a new individual, like to 

 that from which they took their birth : but I acknowledge," 

 says Vaucher, " that I have not seen this separation, although 

 I have no doubt but that it really takes place." 



What Vaucher regards as the young proliferous offspring, 

 are doubtless to be regarded as parasitic growths, to which the 

 Conferva are peculiarly liable, more especially when they are 

 confined for a length of time in small vessels of water. 



Two other species of this group have been referred by 

 Meyen to a genus Hempelia, which he instituted for them, a 

 genus even more erroneously defined than that of Prolifera, 

 already noticed. 



"HEMPELIA. Thallus simplex, membranaceus, septatus, 

 cequalis vel inacqualis. Fructus terminalis est, capsula sub- 



