April, 1915.] The Inheritance of Size in Tomatoes. 
481 
Moisture. The noticeable lack of moisture will cause a 
plant to become ill-nourished and dwarfed. The moisture con¬ 
ditions in the greenhouse were controlled as perfectly as possible 
and the tomato plants were watered quite often, but even then 
optimum moisture conditions did not prevail. The lack of a 
constant abundance of water probably exerted a great limiting 
influence upon the size of plant. The transpiration of water is 
directly proportional to the amount of leaf surface and, after the 
plant has reached a certain mature size, the leaf surface becomes 
limited as the amount of moisture in the pots is limited. The 
plants grown in the garden attained a greater size than the potted 
plants and one of the principal reasons for this difference was the 
more constant and abundant supply of soil-water present in the 
garden environment. There was no corresponding influence 
upon the size of fruit, as there was no noticeable difference of 
fruit-size as a result of the different moisture conditions under 
which the plants were grown. 
Soil. The quantity and quality of the essential nutritive 
substances in the soil, as well as the physical condition, influences 
the size of a plant and fruit. Wanning says (b), “Defective 
nutriment (that is an inadequate supply of one or more substances) 
may be the cause of dwarf-growth (nanism); this has been demon¬ 
strated by many physiological investigations.” All of the 
potted plants in these experiments were supplied with a soil as 
perfectly adapted as possible, both physically and chemically, to 
the growth of the tomato. And yet, the amount of available 
plant nutriment in a five-inch pot is necessarily somewhat limited 
while the available nutriment substances are more abundant in 
the garden, so that this lack of nutriment in the pots together 
with the lack of perfect moisture apparently caused the difference 
in size between the greenhouse and garden-grown plants. There 
was not enough difference, however, between the soil and moisture 
conditions of the greenhouse and the garden to cause any appre¬ 
ciable change of fruit-size. 
Two experiments were tried to determine the effect of different 
kinds of soil conditions upon the size of plant and fruit. 
The first experiment was performed in order to show the effect 
of the garden conditions upon the size of plant as compared with 
the effect of the greenhouse environment upon the size of the 
same plant. In the garden the soil contained more available 
nutriment and moisture than were present in the pots. A number 
of plants of the F-l generation (17-12-2) were grown in the green¬ 
house where they attained at full maturity a height of about 2.5 
feet and a diameter of 1.5 feet. One of these plants was afterwards 
removed to the garden where it grew to be 3 feet high and covered 
(b) See (40) page 56. 
