Mr. HassaH's Notices of British Freshivater Conferva. 337 



On a careful examination, therefore, of the many points of 

 difference here enumerated between the Confervas which I de- 

 nominate Vesiculasperma and the Conjugate, there are but 

 few, I think, who would be inclined to question the propriety 

 of retaining them in separate groups. The differences are too 

 great to admit of their holding merely a generic rank. The 

 naturalness of the genera Zygnema, Mougeotia and Tyndaridea 

 is now generally admitted, although these pass through cer- 

 tain species one into the other, as already pointed out in a pre- 

 vious paper, and are all allied by family resemblances, such as 

 the extreme mucosity and conjugation of the filaments ; but 

 how wide is the interval between any of these and the Con- 

 fervas composing the group of Vesiculasperms ! 



There remains now but one genus of freshwater Confervas, 

 amongst those with simple unbranched filaments, with which 

 to compare the Vesiculasperm<e, and that is the genus Sphm- 

 roplea. We have here the delicate structure and highly mu- 

 cous condition of the filaments so obvious in the Conjugate ; 

 but we have likewise the tapering of the filaments equally 

 characteristic of the Vesiculaspermce, and also the formation 

 of spores without union of the filaments. The genus Sphcp- 

 roplea then, of which I shall speak more fully in a future 

 paper, holds in my opinion a station intermediate between 

 the groups Vesiculaspermce and Synsporce. 



The spores in the different species of the group Vesicula- 

 spermce I conceive to be produced in the same manner as in 

 the true species of Zygnema referred to in the preceding 

 paper as producing spores without union of the filaments, 

 that is, by the intermingling of the contents of two conti- 

 guous cells in the same filament, the one containing in all pro- 

 bability fertilizing, the other fertiiizable material ; this com- 

 mingling being generally and perhaps always accompanied by 

 the inflation of the receiving cell, the primary form of which 

 is invariably more or less ovate, and the giving cell being 

 constantly placed in communication with the narrow end of 

 the ovate inflated cell. 



When a number of inflated cells occur in the same filament, 

 it is a rule that the larger ends of these cells should always 

 point in the same direction. [This union of the contents of 

 two separate cells does not generally take place in so far as I 

 have yet been able to observe in the branched species, although 

 I have ascertained beyond doubt that it does so in one in- 

 stance, viz. in Bulbochcete setigera, the union being followed, 

 as in the other cases, by the inflation of the receiving cell 

 and the formation of a sporaceous mass, whether a true spore 

 or not I am unable to say. Through the genus Bulbochcete, 



Ann. §• Mag. N. Hist. Vol. x. Z 



