INDUCED CHROMOSOMAL ALTERATIONS 



1287 



Table 1 contains some, largely unpublished, results indicating the 

 extent of variation in Xi^ induced in N. Tabacum. The cytological and 

 genetic evidence available indicates that the majority of the striking 

 variations from control in external morphology were the reflections of 

 induced chromosomal alterations of the types referred to. In other 

 words, the data submitted in this table illustrate the frequency of induced 

 chromosomal alteration in this species. 



Table 1. — Variation in the First Generation from X-radiation of Sex Cells. 



Seeds, and Seedlings of Nicotiana Tabacum var. purpurea 



Dosage in each case 50 kv. and 5 ma. at 30 cm., no filter 



Doubtless the extent to which chromosomal alteration can occur 

 in Nicotiana Tabacum without lethality, as shown in Table 1 and as 

 indicated by extensive cytogenetic evidence, is in part a product of its 



^ The designations Xi, X2, etc., and Ri, R2, etc., refer to the successive generations 

 derived from X-ray or radium treatment of reproductive or meristematic tissues. 



