200 BOTANICAL GAZETTE [SEPTEMBER 
A few laterals may extend upward. The main root of a specimen 
18 in. in height was followed along the face of a steep bank for a 
distance of 15 ft., at which point the root was a quarter of an inch 
in diameter. The superficial character of the root system makes 
possible the vegetative multiplication by which the plant maintains 
itself in its unstable habitat. Erosion exposes the roots, which 
, put forth new shoots. 
Discussion 
On account of the 
fact that here, where 
the soil is of fluviatile 
origin, the conditions 
to which roots are 
exposed vary so much, — 
even within the habitat 
determine. Variations 
are common, but they 
may be due to one or 
more of a large number 
of soil factors, such as 
the composition of the 
soil, its penetrability, 
‘Fic. 29-—Galierrezia Sarothae from near bottom its alkalinity, its wilt- : . 
: of arroyo. 
ing coefficient, etc. 
roe problem of the causes of root variation is one to be attacked 
lition: ssa huasasic one factor can be varied at : 
ne Pees ane made apparent the effect of at least two a 
