Hayes and Garber - Cucurbit Breeding

FLAX AND TOBACCO 169
quality of cured leaf is superior to the ordinary varieties.
Comparative
yields show that the Mammoth variety yields 20 to
25 per cent, more than other varieties when grown on productive
soil.
As the Mammoth variety has shorter internodes than
ordinary varieties the leaves shade one another. This prevents
coarse texture and dark colors even on highly productive soil.
The ordinary varieties, when grown on rich soils, yield darkcolored
and coarse-textured leaves. The value per acre of the
Mammoth tobacco is 30 to 40 per cent higher than ordinary
varieties (see Fig. 37).
Garner and Allard (1920) have studied the effect of relative
length of day on growth and development of plants, particularly
with respect to sexual reproduction. By placing a ventilated,
dark chamber in the field the relative number of hours
of exposure to sunlight was controlled as desired. They found
that:
"Normally the plant can attain the flowering and fruiting stages
only when the length of day falls within certain limits, and, consequently,
these stages of development ordinarily are reached only during
certain seasons of the year. In this particular, some species and varieties
respond to relatively long days, while others respond to short days,
and still others are capable of responding to all lengths of the day which
prevail in the latitude of Washington where the tests were made."
In the absence of a favorable length of day for bringing into
expression reproductive processes in certain species, vegetative
development may continue and thus lead to the production of
such varieties as Stewart Cuban and Maryland Mammoth which
under ordinary conditions never reach the flowering stage.
"Thus, certain varieties or species may act as early or late maturing,
depending simply on the length of day to which they happen to be
exposed."
The Stewart Cuban and Maryland Mammoth varieties of
tobacco, as well as several other species were used in a determination
of the effect of reduced length of day in forcing flowering.
In discussing the effects of controlling light as a means of
forcing flowering in Maryland Mammoth, Garner 1
says;
"Under a given length of day favorable to flowering, this type can be
1 From a letter written September 14, 1920.