MUTATIONS IN PLANT BREEDING 367 
varieties grown in this country in 1895 had a similar origin. There is no 
reason to suppose the number has decreased and it is probably larger. 
There is good evidence (see Chapter XIV) to show that bud sports arise 
through factor mutations and that they occur in as great diversity as do 
seed sports. Sometimes striking morphological or substantive changes 
are produced but probably the somatic effect is often slight and hence 
not easily detected (Chapter X XIII). 
Mutations in Crop Plants.—Johannsen has reported two mutations 
in his pure lines of beans. The careful statistical analysis of his successive 
pure line families revealed the first mutant in 1903 and Johannsen thinks 
it appeared as a bud sport. It was characterized by its large size and 
relatively narrow shape. As it was constant from the first it must have 
originated in homozygous condition. The second mutant bore seeds 
which were relatively broad in shape. It could be traced back to 1907 
when it existed in heterozygous condition. Later it was obtained in pure 
line. Very recently mutations of great commercial value occurred in the 
Florida Velvet Bean, Strzolobiwm deeringianwm. The old variety was 
limited to Florida and the Gulf Coast on account of lateness. About 
1,000,000 acres were grown in 1915. Weare informed by Piper that early 
varieties originated by mutation at at least three different places, the first 
in 1906. These resulted in the crop being adapted to the entire cotton 
belt and in a very rapid increase in acreage since 1915. In 1916 about 
2,650,000 acres were grown and in 1917, about 6,000,000 acres. 
Hayes describes a number of mutations in tobacco which is normally 
self-fertilized. The first was found in a homozygous strain of the 
Connecticut Cuban shade variety of commercial tobacco (N. tabacum). 
This strain bears from 14 to 25 leaves per plant, the mean number 
for 1910 and again for 1914 being 19.9 leaves. In 1912 the Windsor 
Tobacco Growers Corporation grew about 100 acres of this strain 
and during the clearing of the field three plants were found that had 
not yet bloomed and which bore a number of uncut leaves. One of 
these was transplanted to the greenhouse of the Connecticut Agri- 
cultural Experiment Station. It produced 72 leaves on the main stem 
and blossomed about January first. All the seedlings grown from this 
plant came true to the new type which differs from the parent strain 
“in having leaves of a somewhat lighter green shade, in a partial absence 
of basal suckers, and in a practically indeterminate growth”’ (see Fig. 150). 
The quality of leaf seems as good as the Cuban and an increased yield 
per acre of approximately 90 per cent. has been obtained, but it is yet 
too soon to know how satisfactorily the new variety will conform to 
trade requirements. Several similar mutants have been found in plan- 
tations of the Connecticut Havana variety. This variety has been 
grown in Connecticut for over 50 years and is uniform in habit of growth. 
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