PATHOLOGIC PLANT ANATOMY 



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149). Four nuclei in one cell is the most we have seen, but it is prob- 

 able that larger numbers occur. It would seem from the studies of 

 Erwin F. Smith, which, however, are incomplete, that most of the cell 

 divisions in crown gall are by mitosis. Frequently, however, there 

 have been found nuclei variously lobed and in process of amitotic 

 division, and this is probably the way in which several nuclei are 

 formed in one cell (Fig. 149). 



Fig. 149. — Nuclear division in crown gall; 1-16, cells showing amitotic (direct) 

 division; 17, mitotic division in which more chromosomes have passed to one pole 

 than to the other. {After Smith, Brown, McCulloch, Bull. 255, U. S. Bureau of Plant 

 Industry, 1912.) 



HYPERPLASIA . 



Virchow in his " Cellularpathologie " (1858: 58) defined hyper- 

 plasia as all abnormal quantitative increase, produced by cell division, 

 and that definition will be adopted here. It is very difficult in practice 

 to distinguish without a careful study between hypertrophy and hyper- 

 plasia, but in the latter abnormalities are produced by cell division, 



