and Experiments on the Keeping Qualities of Boots. 
103 
the plant in its early stages of development. For this reason 
it is desirable that such manures should be well distributed in 
a large body of soil, and not be placed in too close a proximity 
with the young turnip plants. On light sandy soils, potash salts 
in conjunction with phosphatic manures, and a moderate amount 
of ammonia or nitrogen in some form or other, have a beneficial 
effect both upon the yield per acre and the quality of the roots ; 
whilst on soils containing a fair proportion of clay and loam, 
and soils in a fair agricultural condition, potash artificially sup- 
plied does not appear to increase the produce or to improve the 
quality of the roots. 
Unlike superphosphate, salt retards maturity in root-crops, 
and may be usefully employed on free-growing light soils, upon 
which it is desirable to prolong the period of active growth. 
The effect of salt upon roots is to check premature ripening, and 
thus is the reverse of that of superphosphate. 
The preceding remarks, on the special effects of various 
manuring elements upon root-crops, are not made with a view of 
giving practical directions as regards the most suitable manures 
for a crop of swedes, but merely for the purpose of pointing out 
how different is the influence of various manuring constituents 
upon roots, in either promoting or retarding their maturity, and 
generally in affecting their nutritive and keeping properties. 
As regards the differences between sound well matured 
swedes and unripe less nutritious roots, I need hardly state 
that the latter are much poorer in sugar than the former. As 
pointed out already, roots of low feeding-quality are always 
richer in nitrogen than good feeding swedes. Unripe or im- 
perfectly matured roots, as is well known, are apt to scour stock 
even if given in moderate proportions. The precise cause of 
this disagreement of immature roots with the health of stock 
has not yet been thoroughly investigated. It may be that unripe 
roots contain a poisonous principle which does not exist in fully 
matured roots, and the chemical nature of which has not yet 
been discovered. Unripe potatoes, we know, contain Solanine, 
an extremely poisonous substance which does not occur in 
ripe potatoes ; and it is quite possible that a principle belonging 
to the same class of chemical compounds to which Solanine 
belongs may one day be discovered in unripe roots. Or per- 
haps the injurious effects of immature roots are connected with 
the presence of certain organic acids. As a matter of fact, 
we know that oxalic acid, a powerful vegetable poison, occurs 
in unripe roots in small proportions, and in larger quantities in 
the leaves of turnips, mangolds, sugar-beets, &c. ; and it is 
therefore not at all unlikely that, in some degree, the scouring 
effects of unripe roots may be due to the presence of oxalic acid. 
M 2 
