178 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
Eoot development was also made a subject of special inquiry 
in the experiments undertaken under the auspices of this 
Committee at Chiswick, by Dr. Gilbert and myself. In those 
•experiments, which extended over two years, twelve different 
plants were grown under six different conditions of manuring, 
and the results, including the notes on root development, were 
published in the Journal of this Society, 1870 (Yol. III., page 
19 and page 195). 
It stands to reason that a large production of root-fibrils and 
root-hairs exhausts the soil in their immediate neighbourhood 
sooner and more thoroughly than a more limited development 
does. But, on the other hand, it must be remembered that 
long, deeply rooting plants, or plants with thick root-branches 
penetrating downwards to a considerable depth, may, in the 
•aggregate, produce quite as many or more^feeding roots, though 
they may be more widely diffused and not so apparent to the 
eye. These differences are, in a vague general sense, denoted 
by the ordinary terms of “ surface-rooting ” or “ deep-rooting ” 
plants. The surface-rooting plants have usually finely branched 
root-fibres in great numbers, not penetrating very deeply and 
liable to be injured by drought or by frost. The more deeply 
rooting plants are usually plants of longer duration, with 
ooarser, stronger, less branched but much more deeply pene¬ 
trating roots. Such plants therefore are better able to withstand 
drought, first because they are not so much affected by surface 
evaporation, and next because they can obtain supplies of 
moisture from a greater depth. 
It is, however, not my purpose to allude in further detail 
to these subjects here, but, in reference to the changes in 
roots produced by different circumstances, I may, in passing, 
allude to a remarkable change which I have more than once 
observed when growing seeds of oak, filbert, and chesnut 
in bottles of water. In such cases, especially when, owing 
to the non-removal of the cork, the air in the bottle becomes 
somewhat stagnant, I have observed the production of very 
numerous flat, flaky excrescences, spongy in texture, and 
whitish in colour, from the sides of the root and of the stem. 
Under the microscope these excrescences are seen to consist 
of large oblong cells, loosely aggregated, and confined within 
a thin epidermal layer. These outgrowths suggest a resem- 
