184 Humbert. 
I. Influence of Certain Chemical Injections on Variation. 
The experiment which forms the subject matter of Chapter I of 
this paper was planned to give data on the influence which certain 
chemical injections may have upon the amount and range of variation 
in plants, when such chemicals are injected into the young developing 
ovaries. The experiment was suggested by the work of Dr. D. T. 
MacDougal’) of the Carnegie Institution. MacDougal wished not 
only to produce mutations by artificial means but also to study the 
problem of ‘localization of the mutations in the life history of the 
plant”. He wished to determine the exact stage at which the mu- 
tations take place so that the chromosomes might be examined with 
a view to determining what changes occur in them in connection 
with saltations in inheritance. He considered it most probable that 
changes which constitute mutations would take place prior to the 
reduction divisions in the embryosac or in the pollen mother cell, 
and therefor made the injections before fertilization had taken place. 
He divided the chemicals used into two classes: those of high osmotic 
value and those stimulative in low concentrations. The experiments 
on Begonia rotundifolia, with a species of Cleome, and Abutilon 
abutilon were without success so far as the production of new 
types was concerned. Some pedigreed strains of Oenothera lamarc- 
kiana were then treated with copper sulfate one part to four 
hundred thousand parts (1/499909) immediately previous to pollination, 
and the resultant seeds planted in Sept. 1905. A study of the 
plants showed the usual mutations of the species in about the 
normal proportions. O. dennis was next employed. In this species 
magnesium sulfate seemed to be without effect, but where zinc 
sulfate 1/59) was used one rosette was discovered which differed 
greatly from any known form, some of the differences being plainly 
apparent even in the earliest leaves of the seedling. The parental 
form had been under careful observation for five years and no plant 
like the aberrant form under consideration had been noted. The 
plant was plainly a mutation, and supposedly one caused by the zinc 
solution which had been injected into the ovary of the mother plant. 
1) MacDougal, D. T. Discontinuous Variation in Pedigree Cultures. Pop. Sci. 
Mo. 69: 207—225. 1906. 
— — Induction of Mutations. Carnegie Pub. 81: 61—64. 1907. 
— — Heredity and Environic Forces. Science N. S. 27: 121—128. Jan. 24, 1908. 
— — The Direct Influence of Environment. Fifty Years of Darwinism. pp. 114 
—142. 09. 
