VARIATION 319 
remained constant for hundreds of test-tube “generations.” It must 
be admitted that in most of these cases no specific influences can be 
named as the direct cause of the inherited variation. But there is no 
longer any doubt that permanent, discontinuous variations do occur 
spontaneously in these lowest organisms, and it is highly probable 
that certain incidental, external forces play an important part in 
inducing such variations: 
Direct experimental attack upon the germ cells themselves has 
been made with plants by a number of investigators, notably by 
MacDougal, who injected very dilute solutions of potassium iodide, 
zinc sulphate, sugar, etc., directly into the ovaries of various plants 
immediately before fertilization. Consequently somatic changes have 
been produced which were inherited throughout several generations. 
D oO 
Fic. 56.—0O, portion of leaf of Scrophularia showing branching lateral view; 
D, branching vein replaced by two laterals in leaf of seedling grown from seed 
produced by an injected ovary. Also note the difference in size and margin of 
leaves. (From Babcock and Clausen, after MacDougal.) 
By means of check experiments and observations it was found that 
these germinal variations were not caused by the wounding of the 
ovary and it is thought that they must have been induced in some way 
by the presence of the foreign chemical solution in the ovary. Fig. 56 
shows a morphological change which appeared in a seedling of an 
unnamed species of Scrophularia asa result of ovarial injection. Hav- 
ing tested the species sufficiently to determine that it was a simple one, 
MacDougal treated several ovaries with potassium iodide, one part 
in 40,000 and secured 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 plantlets were characterized by a succulent aspect of 
the leaves and by a lighter and yellow color of the leaves and stems. 
