GRAF ZU SOLMS-LAUBACH— MONOGRAPH OF THE ACETABULARIE.E. 10 



It results from the comparison of these courses of development — as also from the 

 similar cases of Botrydium and Vaucheria — with tliosc of most Chlorophycece^ that it is, 

 particularly in the former group, the sexual generations that become rudimentary or 

 eventually disappear, while otherwise this is the case with the asexual. In consequence 

 we find in our group that the vegetative functions become attached to the asexual 

 generation, while usually they are attached to the sexual. 



Possibly the consideration of this phenomenon might throw some light on the peculiar 

 apparently analogous separation of groups among the ArchegoniatcB^ where the Eerns, in 

 their course of development, w^ould correspond with the present group and the Bryinece 

 with the remaining Chlorophyceoj. 



So much for the mutual relations of the genera of Cymopoliece. The Bornetcllece , 

 including only the genus Bornetella, do not enter farther into the question, and we may 

 finally turn to the consideration of the relations which exist among the genera of 

 Acetabulariece. There are two points of view in the disposition of the forms : first, the 

 external development of the fertile plant ; and second, the distribution of the incrusted 

 parts in these. According to the first, Ilalicoryne, with its regular alternation of 

 numerous vegetative and fertile whorls, must be placed apart from all other genera ; 

 according to the second we should have, from the occurrence or absence of incrustation 

 in the interior of the sporangia, at least two if not three groups. One of these contains 

 merely the genus Acetahularia, the other all the remaining genera ; or if not, possibly 

 Acicularia should be separated from the others as a group in which not the spore- 

 membrane as in other cases, but rather a slimy mass within it of uncertain origin is the 

 basis of the calcification. There is naturally no certain proof whether one grouping or the 

 other is the correct one. But I should, after considering all the circumstances, place the 

 mode of calcification in the foreground, especially on this account, — that Halicoryne in 

 this respect agrees so absolutely with Chalmasia. We should then retain the two or 

 three groups mentioned, and the peculiar cap-formation must be taken as occurring in 

 the course of development at different times in the Acetabularidc(E and IIalicorynide(B. 

 That the type of Halicoryne stands nearer the ancestral form of the whole family of 

 Acetahulariece than the cap-forming type of the other genera seems to be supported by 

 its similarity to the more remotely allied types of the Dasycladece, from which it is 

 distinguished by the alternation of fertile and sterile whorls, and besides by the lateral 

 sporangium ; and this alternation we have seen occur in Acetahularia, where this genus in 

 its normal course of development, and not as a monstrosity, produces several discs in 

 succession above each other. This case, only known as yet in A. crenulata, would seem 

 to correspond to a reversion to a Halicoryne-like type. 



Clavis Generum. 



I. Sporse incrustatione calcarea omnino destitutae. Rami fertiles discum umbelli- 



formem constituentes 1. Acetahularia. 



II. Spora incrustatione. calcarea prseditse. 



A. Ramorum fertiliura verticilli plures superpositi. Rami hberi vesiculiformes... 2. Halicoryne. 



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