probnction of air passages in tbe root of Zea 
flDa\>s variation of tbe culture mebia. 
F. DE LA M. NORRIS. 
INTRODUCTION. 
THE following preliminary experiments were madein the Botany 
Department of the University of Bristol during - the Session 
1911-1912, in order to trace a connection between the development 
of, and modifications produced in, a plant by varying- the conditions 
under which it is growing. The root of the plant is perhaps the part 
best adapted for experiments of this nature as it is comparatively 
an easy matter to alter the external conditions of the root without 
introducing into the experiment any factor which is likely to be 
detrimental to the general tone of the plant. 
The plants (Zea Mays) were grown in several different soils and 
media, and in some cases they were germinated in damp sawdust 
and afterwards transferred to water cultures. 
In many of the media the temperature was varied, some plants 
growing at a comparatively high temperature, others at a fairly 
normal one. It was found however on subsequent examination of 
the roots that this temperature variation produced no appreciable 
effect — except in the rate of growth of the plant. 
Experiments. 
The following media were used in the various experiments : — 
(1) Potting soil. 
(2) Sand. 
(3) Damp sawdust. 
(4) Damp clay soil. 
(5) Wet ashy soil. 
(6) Ordinary soil. 
(7) Various water cultures. 
Nature of the Media. 
(1) Potting Soil. — This consists of a mixture of fine soil, sand, and 
leaf-mould. It allows an easy access of air to the roots, 
and is also rich in food material. 
(2) Sand. — This medium allows the root a plentiful supply of air, 
and drains quickly. It is not however very well supplied 
with nutritive substances. 
(3) Damp Sawdust. — This is not a very favourable medium — both 
food material and air being scanty. 
(4) Damp Clay Soil. — This soil drains very badly, and does not 
allow much access of air to the roots ; it is not a favourable 
medium to derive the necessary food substances from. 
(5) Wet Ashy Soil. — This is also very poor in food material ; the 
air has fairly free access to the roots. 
