2. Mutagenic action of nitrogen mustard.

An apparatus was described in last year�s News Letter by which mustard gas vapor may be applied to pollen in accurately graded doses. Continuation of the work with mustard gas has given the following results. Chromosomal derangements leading to partial fertility in the F₁ plants are induced with high frequency in mustard treated pollen. Most of them appear to be deficiencies. Few, if any, reciprocal translocations occur. The relation between dosage of mustard applied to the pollen and frequency of partially sterile F₁ plants is linear. The incidence of readily detectable point mutations relative to sterility‑inducing chromosomal derangements is low. Following pollen treatment the number of entire losses of dominant endosperm characters is much higher in F₁ endosperms than in the associated embryos. Fractional losses of different dominant characters in F₁ endosperms were 1.4 to 4.0 times as high as entire losses.

P. B. Gibson

R. A. Brink

M. A. Stahmann