farr: cytokinesis of pollen-mother-cells 



307 



Arrangement Partition Division by Author Mother-Wall 



" Nichols 



" Cannon 



" Beer thick 



" Shoemaker 



" Pace 



" (see above) 



It will thus be seen that quadrlpartition has been reported in, 

 at least, 32 dicotyledons, 11 monocotyledons, i gymnosperm, 

 6 ferns, i moss, and 5 liverworts. Bipartition in the spore-mother- 

 cells has also been reported in each of these groups, except the 

 mosses; but only 12 cases are noted in dicotyledons, and 18 in 

 monocotyledons. Quadrlpartition by cell-plate formation has 

 been reported most abundantly in the liverworts, due largely to 

 the work of Farmer, and in the ferns. Nine cases have been re- 

 ported among the dicotyledons; they are: in Oenothera by Gates, 

 in Podophyllum by Mottier, in Syringa by Juel, in Lavatera by 

 Byxbee, in Cobaea by Lawson, in Bignonia by Duggar, in Althaea 

 by von Mohl and by Wimmel, and in Cucumis and Tropaeolum by 

 Strasburger. The statements by the writers of some of these 

 papers as to the presence of a cell-plate have been seriously brought 

 into question by more recent work on the same plants. The 

 other papers give no figures which in any way demonstrate the 

 presence of a cell-plate in these divisions. Their evidence consists 

 entirely of statements without confirmatory description or figures, 

 and in view of my results on Nicotiana can not be accepted as 

 final evidence. On the other hand, there is more or less evidence 

 that quadrlpartition occurs by furrowing and without a cell- 

 plate in 21 dicotyledons. In 18 dicotyledons quadrlpartition is 

 reported as accompanied by a thickening of the mother-wall. 

 In none of these has a cell-plate been demonstrated beyond doubt. 

 In fact, no case has been proven in any plant, so far as the present 

 survey of the literature goes, in which quadrlpartition by cell- 

 plates has been found in a cell with a greatly thickened mother- 

 wall. The nearest approach to this is given in Strasburger's 



1 The data in the last column are based upon the authors' drawings respectively, 

 measuring from the outer boundary of the cell wall to the protoplast. 



