500 BOTANICAL GAZETTE [DECEMBER 
response. The formation of the root hair is inhibited by removing 
the covers of the Petri dishes in which the seedlings are growing. 
Regions of no root hairs, corresponding to the growth made during 
the removal of the cover, followed in regions of hair formation at 
the period of its replacement. 
A series of corn seedlings was grown in air of a known moisture 
content. This was controlled by percentage solutions of sulphuric 
acid. The corn was soaked for 24 hours and then hung on cork 
plates in bottles which were one-third filled with the varying 
solutions. The bottles, which were corked and paraffined, were 
all placed in a water bath kept at 24°C. The measurements in 
table V represent in each case the average of 5 sets. 
TABLE V 
Solotion —— ket ane ata mindy root ae ig -_ 
Wat ce a 3.0 70 80 
I ot cent So a 1.0 64 70 
ee 2.0 65 79 
a * 3.0 63 66 
4 “ “ “ 2.0 60 50 
5 « “ « 1.5 70 70 
oo 3 15 60 5° 
ee . 1.5 55 5° 
a * r 1.0 65 60 
9 “ “ “ ye 5 66 41 
eo s 1.0 64 23 
rE Ee ets 2 1.0 61 24 
0 Tag try x 1.0 70 10 
epee as . 1.0 79 10 
Table V shows that the cutting down of the moisture content 
affects the length of the root hair more than the length of the root 
or the diameter. 
2. IN LIQUID MEDIUM 
a) The physical character of the walls —There is a variation in 
the wall of the corn in different media. In moist air the wall is 
uniform; in water when formed the hair is thickened at the tip. 
b) The chemical nature of the walls —The chemical study of the 
walls is under investigation. 
