28 GENETICS IN RELATION TO AGRICULTURE 



of Scrophularia as a result of ovarial injection. Having tested this 

 species sufficiently to determine that it was a simple one, MacDougal 

 treated several ovaries with potassium iodide, one part in 40,000 and se- 

 cured seed. No other species of Scrophularia grew near the cultures. 

 From this seed only three plants were raised. "One formed a shoot 

 fairly equivalent to the normal, finally producing flowers in which the 

 anthocyans were of a noticeably deep hue. The two remaining plant- 

 lets were characterized by a succulent aspect of the leaves and by a 

 lighter and yellow color of the leaves and stems. The flowers on one of 

 the derivatives, as they may be called, were so completely lacking in 

 color as to be a cream-white, this derivative being designated as albida, 

 while the other showed some marginal color and a rusty tinge and was 



designated as rufida Seeds of the original two derivatives 



were sowed in the greenhouse. But one plant of albida, the most extreme 

 departure, survived, while four of rufida were secured." MacDougal 

 compared these second generation seedlings with seedlings from the 

 original stock of the species, noting differences in size and margin of 

 leaves, length of petioles and number of marginal glands. He found 

 that the differences shown by the first generation appeared again in the 

 second generation. Striking as these results appear it must be admitted 

 that it would be difficult, on account of the small numbers of individuals 

 differing from the parent type, to prove satisfactorily to the biome- 

 trician that they were not mutations which would have occurred regard- 

 less of the ovarial treatment. 



What appear to be germinal variations in the tomato have been induced 

 by intensive feeding. T. H. White tested the effect of dried blood, dis- 

 solved phosphate rock, sulphate of potash and iron filings all in excessive 

 amounts, and (with the exception of the iron) in various combinations, on 

 the Red Cherry tomato. The lack of data on control cultures of seedlings 

 from the same parent as the experimental cul tures makes it impossible to 

 compare the actual amount of permanent variation produced. T. H. 

 White states that measurements "show that the plants of the sixth gen- 

 eration grown under the influence of the dried blood are one-third larger in 

 height, length of leaf and size of fruit, than those of the second"; (see 

 Fig. 12). The author concludes that " there can be no doubt . . . that, 

 in the case of Red Cherry treated with dried blood, there is permanent 

 variation to the third generation." If these results are corroborated by 

 more carefully planned and rigidly controlled experiments they will add 

 the weight of scientific proof of a principle in plant breeding long since 

 recognized on empirical grounds, to wit, that the introduction of wild 

 plants into intensive cultivation induces variation. Furthermore, it 

 suggests a possible means for rapid permanent improvement of wild 

 forms with which hybridization may be impracticable. 



