GENETICAL ASPECTS OF SELF- AND CROSS-STERILITY 1 
E. M. East 
With the exception of the war period, the genetical and physiological 
aspects of self-sterility in plants have been under investigation at the 
Bussey Institution of Harvard University for the last twelve years; and, 
as often is the case with material worked intensively, the experiments have 
opened up so many new problems that they will probably be continued for 
several more years to come. The opportunity afforded by this symposium 
for bringing together a summary account of that phase of the work having 
to do with heredity is very welcome, therefore, both because results as yet 
unpublished have thrown new light on the subject, and because the previous 
accounts have been too long and detailed for ready reference. The ex¬ 
periments to be reported on here include only those upon the genus Nicotiana 
which for the last three years have been carried on by Dr. E. S. Anderson, 
who gives me permission to refer to his unpublished records. Experiments 
on some other species which I started four years ago are not yet ready for 
publication; but it may be stated that the data from these later experiments 
are in no wise contradictory to what I shall have to say. 
The self-sterile species used were Nicotiana alata Lk. and Otto var. 
grandiflora Comes, Nicotiana angustifolia R. and P. var. crispa Cav., 
Nicotiana commutata Fisch. and Meyer, Nicotiana glutinosa L., and a 
species believed to be Nicotiana Forgetiana (Hort.) Sand. A self-fertile 
species, Nicotiana Langsdorffii L., was also utilized. 
Both N. Forgetiana and N. alata cross easily with N. Langsdorffii. The 
Fi plants show no evidence of true sterility, i.e ., they form normal capsules 
full of seeds as readily as do either of the parent species. All F\ plants are 
self-fertile; and when selfed produce F2 populations consisting of about 3 
self-fertile plants to 1 self-sterile plant. One may assume, therefore, that 
self-sterility in Nicotiana is due to the presence of the allelomorph of a 
dominant self-fertility factor, F. When a population is homozygous or 
heterozygous for factor F, it is self-fertile; when a population is homozygous 
for/, that is to say when it isff, it is self-sterile. These results corroborate 
those of Compton for Reseda odorata, and have been strengthened by an¬ 
other similar investigation made by Baur on Antirrhinum. 
The other three self-sterile Nicotianas used in the work, N. angustifolia , 
N. commutata , and N. glutinosa, will not cross readily with self-fertile 
species, hence the genetic relationship could not be determined. But from 
1 Read in the symposium on “Sterility in Plants,” at the joint meeting of Section G 
of the American Association for the Advancement of Science, the Botanical Society of 
America, and the American Phytopathological Society, at Cambridge, December 27, 1922. 
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