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JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
cultivators in certain cases, though it is strange that their 
absence in other instances should have escaped comment, if not 
observation. In a Vine border for instance, it is remarkable to 
see how the roots will lay hold of a fragment of any nutritive 
substance, invest it with a dense cobweb-like network of fine 
fibrils from whose surface protrude the minute hairs known 
as “root-hairs.” The substances with which the roots come 
into contact are often insoluble in water, a piece of bone, for 
example, and we must therefore admit from that, as well as 
from other evidence, not necessary to be detailed here, that the 
root-fibrils and root-hairs have the power of secreting some 
liquid which acts as a solvent of the mineral matters of the soil, 
the solution so formed being absorbed into the tissue of the plant. 
Grasparrini was one of the first to draw attention to the root- 
hairs.* This author describes and figures many illustrations 
as seen under the microscope ; he points out inter alia that the 
root-hairs are always unicellular; he further asserts that they 
sometimes exude a mucilaginous and granular matter, and he 
even states that in Poa annua the root-hairs burst or open at 
the extremities by means of a little flap or valve and so liberate 
their contents, but these statements are open to doubt. 
Chatin (Mem. Soc. Nat. Sc. Cherbourg, 1856, p. 5) noted 
the production of these hairs when the roots come in contact 
with any obstacle, the contact with which he considered as 
sufficient to account for their formation. The thin film of 
moisture, however, which is apt to collect around such a body 
is more likely to be a determining cause than mere pressure. 
Mer, in alluding to this subject (Comptes Eendus, March 24, 
1879), also attributes the production of root-hairs to arrest of 
growth caused by some obstacle. In such a case, he says, the 
nutritive fluids are diverted from the growing tip of the root to 
the adjoining tissues and especially to the epidermal cells, and 
hence the production of hairs. But that such explanations do not 
hold good in all cases, I produced evidence to show before the 
committee while this paper was passing through the press, in 
the shape of a Badish which had penetrated a piece of soft 
wood. This had offered sufficient obstruction to constrict and 
distort the root but without inducing the formation of hairs. 
* Gasparrini, Ricerche sulla natura dei succiatori e la escrezione 
delle radice. Napoli, 1856. 
