No. 642] 



VARIATIOX IX DATURA 



31 



A study of the effects of radium rays undertaken in co- 

 operation with Dr. Gager has given results which, al- 

 though in an early stage of the experiment, appear sug- 

 gestive in this connection. Other stimuli are being tested 

 which appear to induce irregularities in the distribution 

 of chromosomes to the pollen grains. It will be a matter 

 of theoretical interest to be able to control experimentally 

 the production of chromosomal mutations. It might also 

 prove to be of considerable economic importance to be 

 able to produce at wdl the full range of chromosomal mu- 

 tants in any plants, especially in those which are propa- 

 gated bv vegetative means. 



To us, one of the most interesting features of the Da- 

 tura work is the possibilitv afforded of analyzing the in- 

 fluence ot individual chromosomes upon both the mor- 

 pliologv and physiology of the plant without waiting for 

 gene mutations. Kvidence is at hand which indicates 

 that cN'erv chromosome iii Datura carries factors which 

 influence the expression of the so-called unit character 

 purple pigmentation. Our work so far we believe adds 

 evidence to the conclusion that th(^ inatiire organism- 

 plant or animal— is not a stnicluif like a child's house of 

 blocks, made up of separate unit chafactrr,-. nor is it de- 

 teiTuined by separate and unrehited unit laetors. It is 

 rather the resultant of a whole series ot interacting and 

 more or less conflicting forces contained in the individual 

 chromosomes. 



I TTFR VTURF (^ITLD 



