102 ZYGOPE1YCE.E. 



simply by the growing together of the two conjugating cells, without 

 contraction, and which do not rest, and (2) hypnospores (resting spores), 

 which are formed by the partition of the zygospores, and which rest (as 

 the name indicates) for a time before germinating. The Zygnemece and 

 Desmidiece have, on the contrary, according to De Bary, spores of only 

 one kind, namely, typical zygospores, in the formation of which a fusion 

 and contraction of the whole protoplasmic contents of the conjugated 

 cells takes place, and which become hypuospores without a preceding 

 partition/' 



Wittrock adds: "To me it seems perfectly clear that De Bary is 

 quite right in saying that the hypnospores of the Mesocarpece are not 

 analogous to the zygospores of the Zygnemece, or in other words, that 

 they are not zygospores at all. The hypnospores of the Mesocarpece are 

 formed by partition, and not by an immediate fusion of the protoplasm 

 of conjugating cells, as the case ought to be with zygospores." 



He then proceeds to refer to Pringsheim's observations on this subject 

 with commendation ('' Jahrbucher " xi., 1877). "The act of conjuga- 

 tion may be divided into two different stages. The first, being properly 

 speaking only introductory, consists in the two cells which participate in 

 the conjugation growing together by conjugation outgrowths, and the 

 septum between the cells thus growing together being resorbed. This 

 part of the act of conjugation is what Pringsheim calls copulation. The 

 second stage consists in an intimate fusion taking place of the proto- 

 plasmatic contents of the conjugating cells. This fusion is effected here 

 in the Mesocarpece principally through the moving of the chlorophyll 

 coloured parts of the protoplasm (the chlorophyllaceous bodies) into and 

 to the neighbourhood of the somewhat widened conjugation canal. This 

 second and more important stage of the fecundation Pringsheim calls 

 connubium. The conjugation having taken place in this manner, its 

 effect appears by the tripartition or quinquepartition of the cruciated or 

 H-shaped cell formed by the copulation. Of the cells formed by this 

 partition, the central one is fertile, the two or four lateral ones sterile. 

 The result of the conjugation is consequently not one cell, but several 

 cells, and not cells of one kind, but of two, namely, one propagative cell 

 (a spore), and around it two or four cells not capable of germination. It 

 would be difficult to find a reasonable interpretation of such a result, save 

 the one suggested by Priugsheim, of its being a sporoearpiwrn, and to me 

 this interpretation seems not only reasonable, but perfectly natural, for 

 although the sporocarpium does here remain on a very low, not to say 

 the very lowest, stage of development, it does, however, already possess 

 the constituent parts of a typical sporocarpium. It has a nucleus and 

 a pericarpinm, or at least an equivalent to one. The nucleus is the 

 single central spore-cell, and the ,pericarpium is represented by the two 

 or four lateral sterile cells.'' 



" If the explanation given above is accepted, the essential difference 

 betreeu these Algae and their nearest relations, Zygnemece and Desmi- 

 diece, might be expressed in the following manner: The result of the 

 connubium in the former is a sporocarpinm (and their spore is conse- 

 quently a carpospore), but the result in the latter is a zygospore." 



Wittrock then proceeds to show that in one species the formation of 

 the spores can take place equally in the manner of Mesocarpns, Playio- 

 spermum, and Staurospermum, equally by tripartition, quadripartition, 

 and quinquepartition, and hence he concludes that those genera are not 

 sound, and that all three should be included under sub-sections of the 

 same genus. We have not followed this suggestion, but have retained 

 Mesocarpus and Staurospermuni as distinct, relying upon the difference 

 of form in the central cell. 



For further details we refer the student to the Memoir from whence 

 the foregoing observations are abstracted. 



