ON THE MIXED HERBAGE OF PERMANENT MEADOW. 
1215 
substances capable of conversion into sucb. The true feeding roots, those portions 
which absorb the watery solutions from the soil, are, as is well known, the minute 
fibrils, and even of these it is the portions near to the distal ends only which 
are active. From the sides of these fibrils often protrude the delicate root-hairs which 
have the same powers of absorbing watery solutions from the soil that the fibrils them¬ 
selves have. These root-hairs vary greatly in number even in the same plant, and 
they differ in dimensions in different individuals, some plants being wholly destitute 
of them. Their number depends upon the nature of the medium in which they are 
placed.* Where the soil is porous and charged with moisture the root-hairs are 
abundant, so much so that they give a white cobwebby appearance to the roots in such 
situations. Their relation to the temperature of the soil has not been properly worked 
out, although it is clear that a relatively warm soil is favourable to their development. 
They are developed on all sides from above downwards. 
The production of root-hairs appears to be influenced by much the same circumstances 
as that of the root-fibrils themselves. Moreover, the root-hairs are often specially 
abundant in the case of seedling plants, containing little or no reserve of water, and 
at the point where growth is going on actively, and a large demand for water and 
nutriment consequently exists. The duration of these minute hairs is often very short. 
Once the necessity for their presence is passed, or the conditions for absorption 
become unfavourable, they shrivel and die. 
So far then as absorption of nutritive matter is concerned, it is the minutest fibrils 
with their hair like out-growths that we have to consider. We know, in a general 
way, that their number is much greater in the same species of plant under some 
circumstances than under others. If they are growing in very fertile, moist, well 
aerated and well drained soil, the production of feeding roots (and of root-hairs in the 
case of the plants producing them), is greater than under opposite circumstances. 
Under such favourable conditions they are short and densely matted, whereas in sterile 
soil they are elongated and produce but few fibrils. The dense leash of feeding roots 
made by trees whose roots have access to water is well known ; as also the network 
of root-hairs formed around any food-yielding substance, such as a piece of leather 
or bone. 
Nobbe and Sachs have shown as a result of well devised experiments, that where 
the fertilizing material was thoroughly mixed with the soil, the root-fibrils were most 
abundant, and relatively few in the intervening less rich portions. The experiments 
were varied in method, but in all cases the results showed that the “ principal develop¬ 
ment of the roots occurred in the immediate vicinity of the material which could furnish 
* “Notes on Root-hairs and Root-Growth,” by M. T. Masters, Journal of Royal Horticultural Society, 
toI. v. (1879), p. 173. [A paper of M. Mer, “ De la constitution et des fonctions des poils radicaux,” read 
before the French Association for the Advancement of Science at Reims in 1880, but of which we have 
only seen a very brief abstract, should be consulted.—Note added, October, 1882.] 
7 Q 2 
