T44 BOTANICAL GAZETTE [FEBRUARY 
In solutions seedlings showed a general tendency for the hair 
development to vary with root development, though the results are 
rather discordant, and more work is required before any conclusion can 
be reached. The roots seem to be able to bear higher percentages of 
saccharose than of lactose, glucose, glycerin, mannite, or modified 
Knop’s solution, a result in accordance with that of Livingston. The 
discordance of results above mentioned may be due, in part at least, to 
the absorption of ‘different chemicals from the different kinds of glass 
in the vessels used, since Benecke found such absorption to influence 
the development of rhizoids in Lunularia. 
The effect of the quantity of food is of importance, apparently, 
because of its influence upon the growth of the root. Seedlings of 
Helianthus, whose cotyledons had been cut off at various distances 
from their insertion, produced different root lengths corresponding to 
the lengths of cotyledons remaining, and the hair development varied 
accordingly. 
The oxygen pressure in water was varied by boiling, with no very 
marked difference in the hair production of corn seedlings. Further 
experiments in variation of oxygen pressure are in progress. 
rom the cases mentioned there appears to be a tendency for seed- 
lings under most conditions to produce a longer or shorter zone of 
hairs, probably on account of the surplus energy provided by the 
stored food. 
The growth of roots is more rapid in water than in air of the same 
temperature (as has frequently been noted), with hair production 1D 
inverse relation; the water condition appears to be produced, however, 
in saturated air. The average length of epidermal cells in water roots 
exceeds that of the same cells in air roots, though the average number 
of cells produced each day appears to be approximately the sat 
under the same conditions. Therefore the increased length, in this 
case at least, seems to be due to greater elongation of the cells of the 
water roots. In the same section there appears in general to ees a 
relation between the length of the cells and the production of hairs; 
the average length of hairless cells being greater than that of cells 
with hairs. 
A retardation of growth when the root tip meets with resistance 
causes the root to kink and produce hairs. If wounded, the growth 1s 
also retarded, and the region immediately behind the tip usually 
becomes abnormally enlarged, and at the same time shows a marked 
tendency to form hairs. 
