480 
The Ohio Naturalist. 
[Vol. XV, No. 6, 
Punnet in 1914 (44) conducted extensive experiments upon 
the inheritance of weight in poultry. He obtained an F-l bird 
intermediate in size between the parents while the F-2 generation 
showed strong segregation. These experiments are still in pro¬ 
gress. His latest report (February, 1914), says that the work is 
not yet advanced far enough to permit of complete analysis, “but 
the nature of the F-2 generation raised last year strongly suggests 
that size depends upon definite factors which exhibit ordinary 
Mendelian segregation.” 
In addition to the experiments above noted, other work of 
like nature has been done within the last few years. No definite 
results regarding the explanation of the inheritance of quantitative 
characters have as yet been obtained. Castle says (6) (March, 
1914), “Although extensive observations upon the subject of size 
inheritance in both animals and plants have been made, they have 
resulted in the demonstration, as yet, of no single clear-cut Men- 
delizing unit character (or factor either). ” 
INFLUENCE OF ENVIRONMENTAL CONDITIONS. 
The influence of environment in the present series of experi¬ 
ments may be considered under four heads. 
Light. The growth of the plants was influenced not only by 
the intensity but by the duration of light. In the tomato plants, 
as in other species, assimilation commences with a certain mini¬ 
mum and increases as the intensity of the light rises until a certain 
optimum is obtained. 
Light that is too strong is injurious. The period of ripening 
of the fruits was shortened in proportion as the optimum light 
intensity was reached. In the winter when both the intensity 
and duration were low the plants ceased to bloom but produced 
normal fruits as long as they did bloom. There is no evidence to 
show that the light conditions present in the greenhouse in any 
way influenced the size of fruit. 
Temperature. According to Warming (b), “Each of the 
various vital phenomena of plant-life takes place only within 
definite (minimum and maximum) limits of temperature, and 
most actively at certain (optimum) temperature; these temper¬ 
atures may even differ in respect to the different functions of one 
species. ” From this it may be inferred that the lower greenhouse 
temperatures in winter may have had some influence in causing 
the tomato plants to cease to bloom, since the lower critical 
limits for reproduction, as with many other species of plants, is 
evidently higher than that required for growth. The various 
temperatures of the greenhouse (45° to 100° F.) came within the 
cardinal points for growth and, as far as could be ascertained, 
seemed to have no appreciable influence upon the size of the fruits. 
(b) See (40) page 22. 
