48o 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-1 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 3^ears. 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 ENVIRONMENT.AL 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 intensit}' 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 j^lants 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 Wanning (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 difterent 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 (4.5° 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. 



