AECHER ON ZYGOGONIUM. 115 



marked, so far as I can see, to stamp its genus amongst the Conjugate 

 with abundant accuracy. 



On referring to Professor de Bary's most valuable work on the Con- 

 jugate, and to his figure of Zygogonium didymum (Rabh.),* one might be 

 almost at first sight disposed to think that my plant (PL IV., Figs. 1, 2, 

 3), was congeneric, if not specifically identical therewith ; but, if de Bary 

 be correct in his appreciation of the characters of his plant — and he is 

 always so accurate that it is difficult to suppose him to be in error in 

 this instance — a more careful comparison will show that they are by 

 no means congeneric. 



It has always appeared to me a course to be avoided, and a system 

 to be deprecated, that of authors employing an old generic name in a new 

 or much modified sense. This procedure necessarily involves the name 

 of the author in whose sense one wishes the name to be understood to 

 be constantly appended, and, to make more certain, it would also seem 

 to require the addition of " not of" (non) — the second author (by name). 

 Even with this precaution, the fact of one name being simultaneously 

 current in two senses appears to me to be calculated to lead not unfre- 

 quently to considerable ambiguity and misunderstanding. 



From the fact, then, that Zygogonium (Kiitz.) and Zygogonium (de 

 Bary) are not by any means one and the same thing, it may be desirable 

 here to explain Kiitzing's genus, and then the other related genus of de 

 Bary ; afterwards to describe the particular plant now drawn attention 

 to, which I think is truly identical with that named Zygogonium lave by 

 Kiitzing, and thereupon to point out its divergencies from either genus, 

 notwithstanding its resemblance to de Bary's, and its seeming identity 

 with Kiitzing's, plant; and finally to indicate what is, I think, no doubt 

 its proper generic location. 



Although de Bary in his quoted work employs the name Zygogonium, 

 he does not do so, as has been mentioned, in Kiitzing's sense. The name 

 Zygogonium is one of Kiitzing's ; and his genus, so denominated, may 

 most briefly be defined by saying that for the most part it comprehends 

 those Zygnemata in which the zygospore is formed in the tube halfway 

 between the two conjugating joints, the cell-contents presenting a doubly- 

 stellate arrangement, but sometimes in a band, or scattered ; whereas to 

 the genus Zygnema, as understood by him, Kiitzing would consign 

 those forms only in which the zygospore becomes formed within one of 

 the parent conjugating joints, the cell-contents of the ordinary plants 

 presenting the doubly- stellate arrangement. Thus Zygogonium (Kiitz.) 

 seems a somewhat heterogeneous assemblage, because it is made to con- 

 tain forms with arrangement of contents like the Zygnemata, along 

 with others in which another arrangement prevails. De Bary, without 

 doubt, is quite right in placing all the forms with the doubly- stellate 

 arrangement of the cell-contents of the joints, no matter whether the 

 spore is formed within one of the parent conjugating joints or in the 



Untersuchungen iiber die Familie der Conjugaten," t. viii., ff. 18, 19. 



