1905] SNOW—DEVELOPMENT OF ROOT HAIRS 29 
and chemical experimentation is necessary. SCHWARZ (75) pp. 
156-7) reports a cessation of hair production. in “concentrated” 
solutions (15 per cent. CaCl, and KNO, and 10 per cent. nutrient 
salts), but no distinction is made between the physical and chemical. 
effects of the solutions. PrTHyBRIDGE (63a, p. 235) found root 
hairs more or less variable in his cultures of inorganic. salts. 
The results of my experiments are too incomplete and inconclusive 
to warrant, detailed publication. Many of the plants died, and often 
an experiment when repeated did not give exactly the same result 
as before. , Some factor or factors seem to have escaped observation. 
A possible variable factor is suggested by the variable results obtained 
by BENECKE (5, p. 24) with Lunularia buds, when he used different 
kinds of glass for the vessels. Considering such sources of error 
my results could only be considered as suggestions for further inves- 
tigation. 
Among non-electrolytes, lactose, saccharose, glucose, glycerin, 
and mannite were used, in normal solutions (1 gram-molecule to 1 
liter of water). Dilutions were made from this, sometimes with 
tap water boiled and cooled in the air and shaken to renew the oxygen 
content, sometimes with unboiled tap water, sometimes with distilled 
water, and sometimes with distilled water redistilled from glass. 
The most convenient methed of experimentation proved to be to 
nearly fill stender dishes with the solutions and to float upon the 
surface of the liquid round cakes of paraffin about one-quarter of 
an inch thick with funnel-shaped holes in which the seeds were 
firmly wedged. This method avoids pins.and the cakes ina measure. 
protect the solution from bacteria. They were easily kept clean 
and could be remelted for each experiment. 
In ten experiments with lactose (nine with sunflower and one 
with corn) five showed variable limits (0.2-0.4 N) for hair growth. 
In 0.5 N solution very little growth of the roots took place, and only 
once were papillae found under the microscope.. The seedling zone 
of hairs grew best in water and diminished with increasing concen- 
tration. : 
In five experiments with saccharose two sunflowers gave o.5 N, 
one o.4 N, and one 0.2 N (with boiled tap, water) as the limit for 
hairs; but the growth was not good. Allowing sunflower roots to 
