462 



BROOKLYN BOTANIC GARDEN MEMOIRS 



value of the various methods employed in inducing responses to con- 

 tact stimulation. Deductions, however, based upon a large series of 

 experiments not included here justify us in stating that surrounding 

 plants loosely and irregularly with twine does not produce the same 

 degree of stimulation or response, as by the more thorough contact 

 derived from the use of other material such as wire netting with a 

 uniform mesh, or, in other words, plants react more pronouncedly to a 

 larger contact surface than to a relatively smaller one, although there 

 probably exists a definite size of mesh which would produce the best 

 result, and this would undoubtedly vary with different species. There 

 appears, however, to exist some difference in the degree of stimulation 

 arising from the same size mesh, as shown by the behavior of some 

 species when the contact is applied to the leaves. The leaves, for 

 example, of the sunflower and corn do not respond so freely as those of 

 tomatoes and the castor bean presumably because the leaf apices 

 are the most sensitive as in the case of tendrils. The latter species, 

 possessing different type leaves, would appear to act differently on this 

 account. 



Table 5 

 Showing Growth of Castor Bean (Ricinus communis L.) in Contact with Wire Netting^ 



The data derived from these experiments are not sufficient to allow 

 of deductions being drawn which would be of any value in determining 

 the relative value of the various-sized meshes in stimulating growth. 

 In some cases where galvanized iron netting with a one-inch mesh was 

 employed, the stimulation appeared to be equally as great as with the 

 two-inch mesh. Neither is it possible by these tests to determine 

 accurately the difTerence in the degree of stimulation which resulted 

 from the use of wires and that from the contact of the plants them- 

 selves. In all cases where single plants were employed they were 

 removed far enough away from one another so as not to touch. The 

 stimulated growth, therefore, was due entirely to the material which 

 surrounded them. On the other hand when plants were grown in 

 such a manner as to touch one another there existed two sources of 

 contact. In the experiment shown in Table 9, six sunflower plants 



^12 plants used. Plants in pairs. 



