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MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



that these pollen-mother-cells whose walls become a gelatinous 

 matrix, like that present in so many animal cells, especially eggs, 

 and whose protoplasts assume a spherical form like the egg cells of 

 many animals, divide in a fashion quite analogous to that of the 

 latter: namely, by a centripetal furrowing of the cytoplasm with- 

 out the formation of a cell-plate. 



The occurrence of the various types of division of the spore- 

 mother-cells of the higher plants, as shown by the data thus far 

 accumulated in the literature, is indicated in the following table. 

 It must constantly be remembered that much of it is introduced 

 incidentally to other investigations and is based on fragmentary 

 evidence. With this in mind the evidence as to quadripartition, 

 arrangement of spores, and thickening of the wall, presented by 

 the early cytologists, who had these things definitely in mind, are 

 quite as dependable as the isolated statements of more recent 

 workers. 



Cell division in mother-cells 



thick 



thin 



thick 



thick 



