188 Humbert. 
new elementary species. Seemingly the balance of the plant has been 
upset and new forms arise in consequence. Two striking facts were 
brought out in the reviews: in MacDougal’s work the same new 
form was produced by various chemicals and even by distilled water 
(which may have been impure, however): In Tower’s paper he states 
that the same experiment (the same treatment) may produce one or 
many forms. Evidently the principle use of artificial stimuli or muti- 
lation is to upset the balance in the plant so that new forms may 
arise in consequence of a new balance. It seems to be but an 
academic statement to say that those treatments that have been 
successful in producing a mutation have affected the germ-plasm 
while those that produce changes that revert to the original type 
have not affected the germ-plasm but only the soma. To be of con- 
sequence to future generations the artificial condition must affect the 
germ-plasm. 
The work of the writer on ‘the influence which certain chemical 
injections may have on variation in plants’ is briefly outlined under 
“Materials and Methods’ of this paper. It will be recalled that some 
fifteen thousand plants were under careful observation throughout 
one season (the life time of the plants) for the purpose of noting any 
mutations which might occur. Approximately one half of these plants 
were from seeds from ovaries that had been chemically treated as 
outlined. The method of injecting the chemical into the ovary and 
the stimulants used were suggested by the work of MacDougal. The 
work was undertaken in the expectation that an extensive experiment 
of this kind would add to the sum of the knowledge along this line. 
The plants under observation were for the most part remarkably 
uniform, which is to say that close scrutiny was necessary in order 
to detect differences of consequence. One striking variation was 
found which was repeated in several parts of the plot, but since it 
was found alike in lines from injected capsules and in lines from 
untreated capsules a full discussion of the type will be taken up in 
another part of this paper rather than in this chapter. Aside from 
the variation just mentioned there were found no types distinct enough 
to be considered as elementary species. The experiment did not 
duplicate the work of MacDougal in the matter of producing new 
forms by the injection method. It may be that Silene is more stable 
than the plants used by MacDougal (especially more stable than 
Oenothera) and is therefore not so easily upset in its chemical 
