126 
Drought of 1870 and 
The difference between the conditions of growth of the chiefly 
perennial (or biennial) plants composing the complex mixed 
herbage of permanent meadow land, and those of an annual, 
like wheat or barley, sown at a stated period of the year in 
arable land, and having a fixed, and in the case of barley only a 
limited time for distributing its underground feeders, and so 
availing itself of the resources of nutriment and moisture within 
the soil, are obviously very great. 
The perennial, or biennial, character of most of the plants 
composing the mixed herbage, would seem at first sight to give 
the grass a great advantage over the corn crops. But observa- 
tion shows, that although the immediately superficial layers of 
the soil may be more thoroughly penetrated by the roots of the 
perennial grasses than by those of either wheat or barley, yet 
it is only a very few of the former, encouraged to great pre- 
dominance only under special conditions, that seem to get any- 
thing like the same possession of the lower layers of the soil as 
the two corn crops. Careful examination has also shown, and it 
is probably generally assumed, that the winter-sown wheat secures 
possession by its underground feeders of a more extended range 
and greater bulk of soil, and consequently is better able to avail 
itself of the supplies of food and moisture existing below a 
certain limited depth from the surface, than the spring-sown 
barley. The Avheat-plant, indeed, has the advantage of making 
root, more or less according to season and manure, throughout 
the winter months, during })eriods of which, at any rate, the soil 
will be saturated with moisture ; and in the case of moderately 
retentive and well drained soils, it will be able to establish its 
independence of rain falling during the period of active above- 
ground growth, very much more than will a spring-sown crop 
like barley. 
But there are other points of distinction between the growth 
of the corn and the hay crops. Thus, most of the grasses, which 
comprise the greater proportion of the latter, flower earlier than 
the wheat or the barley ; and the mixed herbage is cut by, or 
before, the end of June, when very little, if any of it, has arrived at 
the degree of ripeness in which the corn crops are cut. These, 
on the other hand, are not only allowed fully to ripen, but direct 
experiments made at Rothamsted upon wheat have shown that 
a very large proportion, probably about half, of the total dry 
vegetable substance, or of the total carbon of the crop, is fixed 
in it under the influence of the greater power of the sun's rays 
after the time at which the hay crop is usually cut. 
These facts are obviously an element in the explanation of 
another fact, to a certain extent commonly recognised, and which 
a careful comparison of the results of the field experiments at 
