JUNE 28, 1901.] 
ferently. ‘‘Only in Lycopodium,”’ says De 
Bary (Comparative Anatomy, p. 60), ‘‘ can special 
hair-cells be distinguished from the other epi- 
dermal cells of the root.”’ 
Special hair-cells are, however, to be found 
in a considerable range of plants, in which 
they form a rather striking anatomical charac- 
ter of the epiblema. In all the cases which I 
have studied, root-hairs arise from cells dif- 
ferentiated for the purpose at a very early 
stage of the epiblema, and from no other cells. 
The hair-cells areshort, often very short, some- 
times wedge-shaped, possess peculiarly dense 
and deep-staining cell contents, and are dis- 
tributed in a manner determined by the mode 
of origin. They originate from the division of 
cells near the root apex. Of each cell pair 
formed, one becomes a hair-cell and very shortly 
shows distinctive characters ; while the other 
either becomes a single ordinary, much elon- 
gated surface cell, or divides to form several 
such (hairless) cells. In most cases the cutting 
off of hair-cells seems to be a matter of stimulus. 
At times the roots are wholly devoid of hairs 
and hair mother-cells ; at other times the grow- 
ing conditidns —as it would seem—call out these 
structures. 
I find such special hair-cells in Azolla, Isoetes, 
Selaginella, Equisetum, certain Alismales and 
certain Nympheeacece. 
In Azolla pinnata (the only species examined 
by me) the root shows several points of interest. 
The root-cap (as we may call the structure de- 
rived from the original segment cut from the 
outer face of the apical cell) consists of two cell 
layers, except at the apex, where the inner 
layer finally undergoes an extra periclinal di- 
vision. The inner layer for a time coheres 
closely to the root-trunk, which is thus clothed 
with a true epidermis. At the same time the 
outer layer is separated from the inner except 
at the apex, and forms a distinct root-cap 
proper. The inner layer is finally pushed away 
from the root-trunk by the growth of hairs 
arising from the outer layer of the cortex, so that 
at maturity, and even before, the main body of 
the root is quite destitute of an epidermal coy- 
ering. 
The hairs arise in close proximity to the apex. 
Exterior cortical cells divide by a wall oblique 
SCIENCE. 
1031 
to the external surface. The lower of the two 
cells so formed in each case almost immediately 
gives rise to a hair, while the other divides 
transversely to form two, four or eight hairless 
cells. At first the hairs stand in regular zones, 
but ultimately these zones often become more 
or less broken by the unequal multiplication of 
the intervening cells in the different vertical 
rows. 
In several species of Nymphzxa examined the 
hair mother-cells or the hairs themselves were 
found as apparently constant characters of the 
epiblema, alternating very regularly with ordi- 
nary cells. In Nymphza, it’ will be recalled, 
the root is without epidermis (except root-cap), 
the epiblema being merely the outermost layer 
of cortex, the Nymphzeaceze in this respect 
agreeing with Monocotyledons and certain 
Pteridophytes. The hair-cells may develop 
in such a way as to give root-hairs, or they 
may be—under most conditions they commonly 
are—suppressed by the closing together, above 
them, of the ordinary elongated cells. When- 
ever hairs are found they proceed from short, 
specialized cells, early distinguishable not far 
from the growing point. An essentially similar 
condition is found in Brasenia, Cabomba, and 
Nuphar. 
In some Alismales—Sagittaria, Limnocharis, 
Aponogeton—essentially the same phenomenon, 
the production of root-hairs solely from prede- 
termined hair-cells, obtains. Thisis interesting 
in view of the recent discovery of the mono- 
cotyledonous character of one of the Nymphe- 
acez. ‘ 
I purpose in the near future to describe at 
length these and other like cases of root-hair 
formation. 
R. G. LEAVITT. 
THE AMES BOTANICAL LABORATORY, 
NortH Easton, MAss. 
QUOTATIONS. 
SCIENCE AT A WESLEYAN UNIVERSITY. 
THE dismissal of Professor Frank D. Tubbs 
from the chair of natural sciences in Wesleyan 
University, at Salina, Kansas, throws an inter- 
esting light upon the standards of orthodoxy 
in that State. Professor Tubbs is laboring 
under the grave charge of believing in evolu- 
