134 CONJUGATED. 



the globules becoming entangled amongst their filaments 

 render them specifically lighter than the water, and cause 

 them to crepitate under the finger when pressed upon. The 

 presence of these globules in warm weather causes the Con- 

 jugatecB and other Conferva to present a vesicated or bullous 

 appearance, which the older algologists thought to be cha- 

 racteristic of a single species, which they named Conferva 

 hullosa : this appearance is now known to belong to a whole 

 host of Aiya generically distinct — such is the progress of 

 scientific research and knowledge. Dillwyn, in his descrip- 

 tion of Conferva fr acta, observes, that, "after being dried, 

 the Conferva bullosce have been used as wadding for stuffing 

 garments, and made mto coarse household linen." Weiss, in 

 his " Plantse Cryptogamiaj Flor^ Gottingenses," p. 23, relates, 

 that formerly the river Unstrut, after inundating a large tract 

 of country in Upper Saxony, on again retiring into its proper 

 channel, left a great quantity of Conf. bullosa, which having 

 been gathered and dried by the inhabitants, was used by them 

 for stuffing their garments ; but that it occasioned violent pains 

 in their limbs : it was also used for making coarse paper." On 

 some parts of the Continent serious injury bas been done 

 to large tracts of country, by the deposit, on the subsidence 

 of the waters which have covered them for a period, of a 

 compact layer of these ConfervcB bulloscB, which has pre- 

 vented the growth of the grass beneath, and thus deprived 

 the cattle of their food. So great an evil has this been 

 deemed of late years, that commissioners have been appointed 

 to investigate the nature of this deposit, and to endeavour to 

 devise some means to remove and prevent its re-formation. 



M. Decaisne, in his " Memoir on the Classification of the 

 Algoe," has, on grounds wliich, on mature consideration, I 

 cannot regard as satisfactory, separated this group from 

 Agardh's class of zoospores, in which I would retain it ; for 

 certain it is that one division of the group of sunsjiores of 

 M. Decaisne, viz. the true Confervece, are propagated by 

 means of zoospores. 



The numerous species of this group resolve themselves 

 naturally into the genera Zygnema, Tyndaridea, Staurocarpus, 

 Mesocarpus, and Mougeotia. 



