STONE: CONTACT STIMULATION 



465 



were planted, to a height of about lo inches and often less, depending 

 upon the nature of the plant in use. The excelsior was cut in lengths 

 varying from i to lo cm. or according to the nature of the plant 

 employed. Since these experiments were all made in darkness and 

 the plants were in all cases covered with receptacles, such factors as 

 light and transpiration were controlled, and under these conditions 

 the seedlings were dependent largely on the reserved material con- 

 tained in the seeds. There was, however, no contact of the plants with 

 each other. Moreover in this series, the same contact material was 

 used throughout, namely excelsior, and any specific reaction which 

 might arise from the use of different materials in contact with the 



Table io 



Showing Growth of Horse Beans {Vicia Faba L.) in Contact with Excelsior^* 



Experiments 



(a) Normal 



Contact excelsior 



{b) Normal 



Contact excelsior 



(c) Normal 



Contact excelsior 



Average normal 



Contact 



Average Height and Weight in Centimeters and Grams 



No. of Plants 

 Used 



149 



374 



Height 



Weight 



14.03 

 18.20 



15.10 

 18.50 



17.32 

 20.41 



0.96 

 1.28 



0.74 

 1.05 



1.37 

 1.50 



Percentage Gain by 

 Contact 



Height Weight 



29% 



18% 

 17% 



33% 



41% 



9% 



15.48 

 19.03 



1.02 

 1.61 



23% 



58% 



Table ii 



Showing Growth of Hypocotyls of Lupines {Lupinus albus L.) in Contact with Excelsior. 

 Average of Two Experiments with 128 Plants^^ 



Average Height of Hypocotyls (Centimeters) 

 Percentage Gain 

 Hypocotyls by Contact 



Normal 19.28 



Contact excelsior 21.65 12% 



plants would not be present in these. There would of course occur 

 variations in the stimulus imparted to the different species owing to 

 difference in the relative degree of contact of the plants with the 

 excelsior — a feature which would be determined by the fineness, 

 compactness and amount of the excelsior employed, as well as by the 



1" Experiments in which light was excluded. 

 '^ Experiments in which light was excluded. 



