16 BOTANICAL GAZETTE [JULY 
and KRABBE (33, p. 474) found roots to absorb less water at low 
temperatures. VAN RYSSELBERGHE (70a) considers that merely 
the rate of absorption is affected by the impermeability of the proto- 
plasm. Devaux (11, p. 52) considers temperature to be of great 
importance in the production of root hairs, but has as yet merely 
‘made that preliminary statement. ScHWARz (75, p. 158) reports 
that optimum temperatures (27-28° C.) do not overcome the inhib- 
itory effect of water, as the roots grow smooth. 
A comparison of the increase of surface in the cases of mustard 
and radish shows that temperature variations of small amount 
have no appreciable effect. The effect of greater changes was tested 
with seedlings of wheat and corn. These were placed in water at 
temperatures of 33-38° C. No hairs appeared on the parts in 
water, while the parts in air, as the height of the water varied a little, 
produced a few hairs. 
Wheat seedlings in warm water, in water at room temperature, 
and in cold water, grew in all three conditions, and gave the following 
results: 
Condition | Temperature | Duration | Result 
CNG cue 4:5-15.5° © ave 26" Dec. 8-18 | Haired to the tip, long and close 
(once 22.5) set ~ 
Medium..... 16.0-29.5° av. 23.7° ec. 8-21 | Hairs not so good, long bare 
spaces at ti 
Warn 5... «< 27-0-48.0° av. 34.5° | Dec. 8-14 | Only two lived, smooth 
Corn seedlings at temperatures of 29-37° (av. 33-4°) produced | 
no hairs; while control plants at 16-27° (ay. 22.9°) were haired at 
first, but later the root assumed its usual water type. This experi- — 
ment was repeated many times with various modifications, and gave 
the same results. 
That the smooth condition was due to the growth, rather than to 
the direct action of the heat upon the epidermal cells, was suggested — 
by the following experiment. Corn seedlings were fastened in tap _ 
water of temperature 18-20° C., which was kept flowing in.a very 
small stream from a rubber tube reaching the bottom of the jar. 
Under these conditions all the roots grew smooth and straight, omit- 
ting the seedling zone of hairs. Whether this was from the constant 
ee ad 2 
bea 
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Fe ne ee pe act TEE Ss 
