260 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



the protoplasm in the oogonia of Fiicus, where there are eight 

 nuclei, each of which becomes separated at the same time from 

 the others by plasma membranes; that is, there are no divisions 

 of the cytoplasm during the three preceding nuclear divisions. 

 They describe the process as beginning by the elongation of the 

 eight nuclei and the development of polar radiations. The di\i- 

 sion planes themselves are marked by the accumulation of granules 

 which are repelled equally from all nuclei. These granules fuse 

 into plates which divide the protoplast into its eight respective 

 parts. The authors refer to the process as due to a repulsion of 

 material from the nuclei, but it may as well be considered an ordi- 

 nary diffusion of material away from the nuclei. It is then essenti- 

 ally like the cell-plate formation in higher plants, except that a 

 central spindle is absent. It will be noted that this is also an 

 instance of simultaneous partition as in Sphacelaria and Dictyota. 

 Fucus is not the only alga in which the division of a protoplast into 

 more than two parts has been studied. Strasburger (67a) noticed 

 the quadripartition of the zygospore of Craterosperniiim [Mougeotia], 

 by ring-shaped primordia of the cross- walls, that is, by infolding and 

 constriction in a centripetal manner. A more lucid description 

 was given by Berthold (6) in 1886 of tetraspore formation in the 

 red alga, Chylocladia. Here we have the partition into four 

 spores which are tetrahedrally arranged by "sechs dement- 

 sprechend orientirte Membranleisten welche, wie bei Spirogyra, 

 allmahlich von der Zellperipherie nach innen vordringen." No 

 cell-plate is involved in the process. Unfortunately no figures of 

 the cells in division are given. 



c. Cytokinesis in the fungi. 

 Division by cleavage furrows without the formation of a cell- 

 plate is the common method among the fungi, as Harper has 

 shown in many forms. There is the simple bipartition of a 

 two-nucleate cell, as in the conidiophores of the Erysiphcae (28a) 

 the more complex " progressive cleavage " of the multinucleate spor- 

 anges, and also of the Mucorineae, etc. (28c). Careful study and 

 search has revealed no evidence of the formation of a {partition 

 plane or cell-plate in advance of the cleavage furrow, the only differ- 

 entiation which takes place, being in certain cases the appearance 

 of a clearer hyaline zone, instead of a dense protoplasm, just in 



