

1915] 



MACDOUGAL — MODIFICATION OF GERM-PLASM 265 



began in 1909, the treatments were made in 1911, and now first 

 and second generations of the derivatives are alive, as well as 

 the original stock. 



Much irrelevant comment and inconclusive experimentation 

 has followed the original announcement of the discovery of 

 the methods used in this work. The necessity for a careful 

 genetic analysis of the material for treatment has already 

 been noted, and it may be well to call attention to some of the 

 features of operation which might appear simple, yet are not 

 easily carried out. No better way has yet been found for in- 

 troducing solutions into the region of the embryo-sac than by 

 injection into ovaries with an all-glass syringe fitted with gold 

 needles (14 karat). The wounding of the ovary produces 

 abortion in some species, and in almost all treatments some of 

 the ovules are crushed. This, however, is a matter of no mo- 

 ment if some reached by the reagent survive and come to 

 maturity. The extent and mode of diffusion of the reagent 

 is in fact one of the most important features of the treatment, 

 and the experimenter will do well to make control tests for the 

 purpose of finding out whether or not there is some possibility 

 of success. 



A test of the ovaries of Carnegiea previously described 

 showed that the liquid was taken up by the placental vessels 

 and conducted to a point near the egg cell in a very short time 

 if the reagent were introduced into the ovaries of flowers fully 

 open and mature. Operations made at an earlier stage re- 

 sulted in the accumulation of the reagent in the inner walls 

 of the locule, in the integument of the ovule and especially at 

 the micropylar orifice. The pollen tube would be subject to 

 the action of the accumulated substance in the micropyle and 

 integument in this case. 1 



It being my present intention to extend experimentation in 

 the Scrophulariaceae, tests have been made with methylene 

 blue in the ovaries of Penstemon Torreyi, the solution being 

 one part of the dye to ten thousand of distilled water. 



1 MacDougal, D. T. Alterations in heredity induced by ovarial treatments. 

 Bot. Gaz. 51:241-256. 1911. 



