186 Humbert. 
some are already displayed by members of the Genus, while some of 
the progressive and retrogressive changes seem to be taken before 
any relative had moved in the same direction. 
Mention was made of the fact that methyl-blue was used as 
one of the injection chemicals. This was done for the purpose of 
studying the mechanics concerned in the changes which injections 
may cause. It was found that the dye is taken up not only by the 
tissues of the ovary but that the pollen tube before it reaches the 
ovary also takes up a considerable amount. It is of course to be 
inferred that the other injections were taken up to a similar degree. 
The generative nucleus must therefore pass through tissue that is 
impregnated with a foreign substance before it becomes effective in 
the ovary. Changes (mutations) therefor may be caused by the in- 
fluence of the chemical on the ovules, or on the sperm or both and 
the change may be before or after the reduction divisions of the 
embryo-sac. The changes may be due to the stimulative effect of 
the solution used or perhaps it may be that a direct disturbance of 
the chemical balance of the chromatin and plasma is effected. 
The work of Dr. MacDougal is the only bit of research found 
which bears directly on the problem named in the title of this chapter. 
Because of this it is given somewhat in detail. In all injection work 
of this nature an attempt is made to affect the germ-plasm of the 
plant directly instead of working on the somatic tissues of the plant 
as so many experiments on “influence of environment” and ‘‘inheritance 
of acquired characters do’. There are however several pieces of re- 
search which attempt to produce mutations by artificial means so 
closely related to the injection work that they should receive brief 
mention here. Such papers include those of Tower!), Blaring- 
ham2), Gager°®), Knox4) and Klebs5). The two latter are somewhat 
from the standpoint of “inheritance of acquired characters’. 
Prof. Tower has worked for more than twelve years on beetles 
of the genus Zepfinotarsa, subjecting them to various combinations of 
1) Tower, W.L. An Investigation in Evolution in Chrysomelid Beetles of the 
Genus Leptinotarsa. Carnegie Pub. 48. 1906. 
2) Blaringham, L. Mutation et Traumatismes. 248 pp. 1908. 
3) Gager, C.S. Effects of the Rays of Radium on Plants. Mem. N. Y. Bot. 
Gar. Vol. IV. 1008, 
4) Knox, Alice A. Induction, Development, and Heritability of Fasciations. 
Carnegie Pub. 98: 1—20. 08. 
5) Klebs, Georg. Über die Nachkommen künstlich veränderter Blüten von 
Sempervivum. Sitzungsber. d. Heidelberger Akad. d. Wiss. 1909. 
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