farr: cytokinesis of pollen-mother-cells 283 



The paper contains no discussion of this pecuHar situation. Shoe- 

 maker (64) in Hamamelis shows tetrahedral quadrlpartition with 

 an incipient furrow in figure 31. The mother-wall is much thick- 

 ened, and no cell-plate is indicated. Miss Eraser (20) in her 

 figure 31 of Vicia indicates tetrahedral quadrlpartition; spindles 

 are shown, but no cell-plates; the plasma membranes are rather 

 indistinct, but there are indications of equatorial cleavage furrows. 

 Miss Digby (136) in her figure, 42, oi Primula indicates tetrahedral 

 quadrlpartition with broad furrows on both sides, which are, 

 however, not exactly equatorial. No cell-plates are shown. In 

 figure 67 the mother-wall is shown to be greatly thickened after 

 the division is complete. She writes, "The cytoplasm between 

 the nuclei constricts," but she makes no reference to the presence 

 or absence of a cell-plate. Miss Nichols (49) reports tetrahedral 

 quadrlpartition, in which the cytoplasm "constricts." Her 

 figure 39 shows such a condition, but there are only two, nuclei 

 shown. Gregory (25) figures for Lathyrus a constriction of the 

 protoplast after the heterotypic division. This he states is 

 accompanied by amitosis and is related to sterility of pollen. He 

 evidently regards it as abnormal, as he says that in the fertile 

 pollen the division is "of the usual type." Cannon (10) in his 

 paper on hybrid cotton shows quadrlpartition in figure 14. In 

 figure 16 he shows division taking place between two nuclei by a 

 broad cleavage furrow; no fibers or cell-plate are shown in the 

 cytoplasm. Of the process he says, "Indentations appear in the 

 periphery of the cytoplasm and midway between the nuclei, which 

 deepen into constrictions, and finally accomplish the separation 

 of the nuclei and the formation of the tetrads." He, however, 

 does not discuss the existence of a cell-plate. 



The figure which best indicates quadrlpartition by cleavage 

 furrows is that of Beer {Sb) on Crepis; unfortunately this is un- 

 accompanied by description. He reports quadrlpartition in 

 Matricaria Chamomilla and Crepis taraxacifolia. Three figures of 

 the latter and one of the former indicate this. In Crepis the 

 mother-cell-wall is slightly thickened, and the nuclei are appressed 

 to the plasma membrane before the cleavage furrow is well de- 

 veloped. No cell-plate is shown; but figures 57 and 58 show a 

 constriction at different stages of development. The relation of 

 the mother- wall to the furrow is not shown. Tahara (69) in his 



