VI 



as 



COMMERCIAL VARIETIES 



in 



takes place through seed mixture is relatively 

 unimportant in comparison with contamination of the 

 ovaries by foreign pollen. We have already laid emphasis 

 on the external similarity of the different varieties, and its 

 bearing now becomes apparent. A field grown under the 

 name of Afifi might consist in reality of a mixture of five 

 or six varieties with the original stock, together with all 

 possible combinations and permutations of their multi- 

 farious gametes, but the difference would be almost 



Length of Lint in mm. 



30 35 25 30 35 



Two Pure Strains. 



Two Commercial Varieties. 



FIG. 50. THE IMPURITY OF -COMMERCIAL VARIETIES. 



Target-diagram plotted from random single plant samples in 1911. 



Identical treatment, site, cultivation (wide-sown) and methods. 



Compared in respect of only two important commercial characteristics. 



o = Variety-type, under given conditions. 



invisible till the bolls opened. The mere fact that such a 

 cotton as Yannovitch was a simple single-plant isolation 

 from Afifi demonstrates this statement sufficiently without 

 resort to our detailed tables of plant to plant differences 

 (e.flr., Fig. 50). 



Further, although the author has quoted Egyptian 

 illustrations, the same arguments apply to American 

 Uplands, to Sea Islands, and to the few Indian cottons 

 which he has studied. Mr. H. Martin Leake has 

 demonstrated exactly similar heterogeneity in both 



