STONE: CONTACT STIMULATION 469 
TABLE 16 
Showing Growth of Roots of Lupines (Lupinus luteus L.) in Water Containing Excel- 
stor and Sphagnum Moss 
Average Length of Primary Roots (Centimeters) 
Treatment Roots 
IN GEitial os tno coe Ae 7.3 
Spharnummosse eee ae ee 8.8 
Excelsioncoarse.4-6 see 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 I7 
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 
INvaynaierl ie 2 See Se rete ware ile 4.5 
Excelsiot coarser rin ean LOr 7.0 
xcelsion fine sae ete ae er Fier 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 
16 5 plants used in each test. 
17 One hundred and sixty plants used. 
