STONE: CONTACT STIMULATION 469 



Table i6 



Showing Growth of Roots of Lupines {Lupinus luteus L.) in Water Containing Excel- 

 sior and Sphagnum Moss^^ 



Average Length of Primary Roots (Centimeters) 

 Treatment Roots 



Normal 7-3 



Sphagnum moss 8.8 



Excelsior coarse 10.4 



For the purpose of obtaining more uniform conditions for root 

 growth, we subsequently adopted larger containers provided with 

 loose partitions, in which case all the plants were subject to like con- 

 ditions. The excelsior experiments were made in either glass or 

 earthen jars with tap water which had been previously boiled to 

 exclude the air. The excelsior, which was of the ordinary commercial 

 form, was in long strands of more or less irregular shape and in cross 

 section was about i mm. in diameter. We employed three different 

 grades, namely, the coarse, loose, curly form as it is obtained com- 

 mercially, and the same cut from i cm. to 4 cm. long. The uncut 

 grades were packed loosely in the jars containing the water, while 

 the finer grades were much more compact and greatly increased the 

 contact surface to which the roots were subjected. In all cases the 

 excelsior was boiled before using it to exclude air, inasmuch as the 

 presence of air would be capable of modifying growth. The seeds 

 employed were of a good quality and were separated by sieves and 

 carefully selected before planting, which insured a uniform size and 



Table 17 



Showing Growth of Stems and Roots of Peas {Pisum sativum L.) in Water Containing 

 Excelsior. Average of Four Experiments^'' 



Average Length of Stems and Primary 

 Roots (Centimeters) 

 Treatment Stems Roots 



Normal 1 1.2 4.5 



Excelsior coarse 10.3 7.0 



Excelsior fine il.i 8.8 



Secondary roots predominated in the fine excelsior, many in the coarse excelsior, 

 practically absent in the normal. 



corresponding germinating capacity. The experiments were con- 

 ducted in a dark place, although in this series not in absolute darkness. 

 The amount of light, however, which prevailed was insufficient for 

 photosynthesis or for phototropic curvatures. Neither the stems nor 

 roots were in contact with one another, hence, any stimulating growth 



1^ 5 plants used in each test. 



" One hundred and sixty plants used. 



