410 
RICHARD M. HOLM AN 
maintained as nearly as possible at the point of water saturation, 
uniformly moist sawdust, and fine-sieved garden earth. In some cases 
the primary roots were decapitated before the appearance of the 
secondary roots (15 centimeter roots were cut to 11 or 12 centimeters), 
in other cases the main roots were not decapitated. In any single 
experiment, however, all the seedHngs were treated alike. Compact 
sawdust was not employed as in the case of experiments with primary 
I 1 
1mm. 
Fig, 2. Two secondary roots of Vicia faba var. equina which arose from a 
primary root planted horizontally in loose moist sawdust and grew obliquely up- 
ward through that medium, maintaining a curvature of the extreme tip. 
roots because the secondary roots always followed a very sinuous course 
in that medium as did also the slender primary roots of Vicia sativa L., 
Ervum lens and other species. This was no doubt due to the mechan- 
ical weakness of the roots and the resistance of the particles of the 
sawdust (which were considerably larger than those of the soil used) 
to the advance of the root tip. In loose sawdust and in soil, neither 
the very irregular curvatures which took place in compact sawdust 
nor the slight "wellenformig" curvatures which Sachs^ observed in 
* Sachs, 1. c. p. 611. 
