256 Heterokontce 



species the chromatophores are few and irregular, but more often 

 they are numerous and discoidal. Asexual reproduction takes 

 place by the formation of globular or ellipsoidal aplanospores, 

 which escape by the breaking up of the filament (fig. 121 B and I); 

 also by zoogonidia with a pair of unequal cilia (fig. 121 C). 

 Sexual reproduction occurs by the conjugation of isogamous 

 gametes, but the conjugation is not strictly isogamous, as one 

 gamete comes to rest and rounds itself off before another swarms 

 up to it and conjugates with it. The structure of the cell-wall of 

 this genus was well described by Bohlin 1 , who also demonstrated 

 the close affinity between Tribonema (Conferva Lagerh.) and 

 Ophiocytium. 



Concerning the abandonment of the generic name ' Conferva,' 

 I cannot do better than quote at length the remarks recently 

 made by Hazen 2 . He writes: 



" The name Conferva is very ancient, going back to the time of Pliny. As 

 a modern generic name it has received most varied treatment, and covered at 

 different times very diverse groups of plants. 



"Under this name Linnaeus included a very large part of the branching, 

 as well as the simple, filamentous algae. He adopted the genus from Dillenius. 

 The first species mentioned by Linnaeus, Conferva ripularis, is undoubtedly 

 the oldest of his group, so far as the history of these ill-defined forms can be 

 determined. This species, according to the synonymy of Linnaeus (Sp. PI. 

 1164. 1753), is Conferva fluviatilis, sericea vulgaris et fluitans of Dillenius 

 (Hist. Muse. 12, pi. 2, f. 1. 1741) ; this in turn is Conferva Plinii Dillen. (Cat. 

 Plant, sponte Gissam nascentium, 199. 1719); the earliest description of 

 C. Plinii that we have seen is in L'Olfel's Plantarum Observationes, 664. 1576, 

 but undoubtedly the name is of more ancient origin. 



"Now no one would imagine that the ancient herbalists or even Linnaeus 

 could distinguish the numerous filamentous forms known to us only by the 

 use of good microscopes. Indeed, the fact that Linnaeus described only two 

 unbranched species is sufficient proof of this. Conferva rivularis as collected 

 by him, was very likely at one time a Spirogyra and at another time an 

 (Edogonium. This type species, however, as interpreted by the earlier 

 algologists, e.g., Dillwyn, Lyngbye and Mueller, is evidently a form belonging 

 to what is now known as Rhizodonhun, and has come down to us as R. rivu- 

 lr'ts (L.) Kiitz. This identification is also confirmed by Linnaeus himself, 

 who (Sp. PI. Ed. 14. 1784) quotes the figure of C. rivularis from Flora Danica. 



"At any rate, there is no warrant whatever for employing the name Con- 

 ferva to designate the genus recognized under that name in Lagerheim's 

 revision, for there is no evidence that these species were ever collected by 



1 Bohlin in Bihang till K. Sv. Vet.-Akatl. Handl. 1897, Bel 23, no. 3. 

 - Hazen in Memoirs Torr. Bot. Club, xi, 1902, no. 2, pp. 181183. 



