THE DEVELOPMENT OF ROOT HAIRS. 
CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 
LXXIV 
LAETITIA MoRRIS SNow. 
(WITH PLATE I AND SIX FIGURES) 
INTRODUCTION. 
EXPERIMENTATION upon the effect of external agents on th 
development of root hairs is complicated by the fact that whe’ 
external conditions are varied the internal factors are disturbed b 
an unknown amount. The varying of only one condition, whi 
is the essential feature in accurate research, was thus extremel 
difficult, if not impossible. Therefore, the results to be set forth 
here are understood to be tentative. The last experimental worl 
upon the immediate subject is that of ScHwarz (75), to which the 
reader is referred for most of the earlier literature. Apart from thre 
or four papers, the references to the causes for the development 0 
root hairs are found incorporated, here and ioe in reports on root 
gestions as to the causes for the production of root hairs, variation: ns 
in their structure not being considered. 
LIGHT AND DARKNESS. 
In view of the fact that in darkness there is generally an inc! 
in the length of the axial organs and of their component cells 
p- 64; 37, p- 254), and because authors differ as to the effect of - 
and darkness upon the development of root hairs, it — 
to reinvestigate the matter. ScHWARz (75, p. 163) reports no é 
Went’s (85, p. 8) experiments were not very convincing one 
or another; DEvaux (10, p. 306) finds that light retards 
and favors the development of root hairs; PETHYBRIDGE 
p- 235) reports that light retards the production of hairs u 
roots of oats and wheat growing in water cultures. The last « 
ment was repeated several times, but very little difference w 
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