24 INTRODUCTION. 



the other during the slow emanation of the matter from the 

 giving filament, and no trace of other motion is observed 

 amongst them. On the contrary, it is in the elliptical body, 

 constituted by the mingled contents of two joints, that I 

 believe to have recognized a phenomenon of locomotion 

 analogous to that described previously in reference to Con- 

 ferva cerea. After many fruitless researches, made for the 

 purpose of seeing the elliptical body develope itself into a 

 new filament, as Yaucher has described, I clearly saw them, 

 on the contrary, dissolve into numerous sporules, endowed 

 with a very rapid motion. Apart from the phenomenon of 

 union of the filaments, which distinguishes the Conjugates 

 from all other Alga, the only peculiarity in their propagation 

 is, that the elliptical bodies from which the sporules proceed 

 remain after many months without any change in them, 

 while they dissolve immediately in the true Conferva" My 

 own view of the nature of these elliptical bodies precisely 

 coincides with that of Agardh. They are to be considered, I 

 think, as so many sporangia stored with zoospores, which 

 they retain together and preserve from injury until the 

 period proper for their developement arrives. Each of them 

 is composed of at least two, and, according to Meyen, three 

 membranes, these being formed by the gradual inspissation 

 of the organic mucus enveloping the zoospores. At all 

 events, if they be not sporangia, and if they ever germinate, 

 as some suppose, but which I consider still to be very ques- 

 tionable, a second mode of reproduction, which some have 

 contended for, must be conceded to those plants possessing 

 them ; for it is very certain that the Vesiculifera^m the different 

 species of which are formed bodies in all respects analogous 

 to those of the Conjugate, are propagated principally, if not 

 exclusively, by zoospores. This is undeniable, and it is but 

 consistent with analogy to suppose, as Agardh has asserted, 

 that the Conjugates are perpetuated in the same manner. 

 The observation that they dissolve immediately in true Con- 

 fervce, does certainly not apply to the true oval or circular 

 organs formed in the true Conferva, with the existence of 

 which Agardh was not acquainted. These are, in all respects, 



