ON THE MIXED HERBAGE OF PERMANENT MEADOW. 
1253 
The roots seldom or never produce such a dense mass of fine fibrils as do those of 
the grasses, but the underground stocks if less finely branched penetrate deeply or 
spread widely. Their fibres, which are usually thicker than those of grasses, are very 
generally provided with little tubercles or nodules. Microscopic examination of the 
tubercles in Trifolium repens has shown us that they consist of an epidermal covering, 
investing two or three layers of cortical cells, within which is a circle of very minute 
fibro-vascular bundles with delicate spiral vessels. The central portion within the 
vessels is occupied by a large mass of cellular tissue, the innermost cells of which are 
larger than the outer polygonal, and often containing lt crystalloid ” contents, perhaps 
of aleurone or of some albuminoid substance. The fibro-vascular bundles are directly 
continuous with the vascular cylinder of the root fibre. There seems, then, no doubt, 
that these nodules are modified root fibres.* When fully formed no root-cap is visible, 
nor is this surprising, as their function seems to be not to extend the growth of the 
root but to furnish a magazine of nutritive matter. For the same reasons, probably, 
all the specimens that we have examined have been entirely destitute of root-hairs. 
[Owing to the peculiar conformation of the flowers, the intervention of insects 
becomes almost absolutely essential to the fertilisation of these plants, as illustrated 
by Mr. Darwin’s remarks on the interdependence of the red-clover, humble-bees, 
field-mice, and cats.] 
Although the occurrence and amount of leguminous species materially affect the 
quality of the mixed herbage of meadow land, and are very dependent on the manu- 
rial conditions supplied, the proportion they contribute to the total produce is 
comparatively small, even when they are considered to be well represented. Indeed, 
if we were to attempt to represent the predominance of the leguminous species in the 
total mixed herbage , it happens that the most prominent of them would only once be 
first in predominance among the total species on the plot. It is, therefore, necessary 
in the tables of predominance to show those which take the first, the second, or the 
third place among the total leguminous, and not among the total mixed herbage of 
the plot. It is essential to bear this in mind in looking at the tables, otherwise the 
frequency with which one or other of the four leguminous species occurring in any 
material quantity on the plots appear as first, second, or third, would be quite 
misleading. The columns showing when the respective plants contributed 5 per cent, 
or over to the total produce, clearly show, by the very few entries, and the many 
blanks, the relatively small proportion of such herbage. 
* See W oeoniN, Ann. Sc. Nat. 5me. ser., vol. 7, p. 84, tab. 6, who shows that these tubercles are asso* 
ciated with the presence of Bacteria, but in our experience they may occur without them, at least it is only 
occasionally that we have been able to detect them. The subject of root tubers has attracted the more 
attention of late from the presence of somewhat similar nodules on the roots of vines affected with 
Phylloxera, but the resemblance to the leguminous tubercles is merely superficial. Other similar swellings 
have been attributed to the presence of a myxomycetous fungus. 
MDCCCLXXXII. 7 X 
