15 
The Causes of Cracking and Remedies.—The formation of 
growth-cracks is a phenomenon familiar enough to gardeners, 
and is of common occurrence not only in root crops, but in fruits 
such as apple, pear, and cucumber. In the pulpy fruits of plum, 
cherry, and tomato a cracking of the skin is also frequent, and 
-in this case, as in the parsnip, decay results. 
Cracking is brought about by an unequal growth in the struc- 
tures concerned; the inner tissues grow more rapidly, and ulti- 
mately rupture the outer layers. In the case of the pulpy fruits 
mentioned, cracking may be partly due to excessive turgidity of 
the inner cells. In either case it is, as a rule, due to the effect 
of,an abundant supply of water at the root after a dry period, 
but at times it appears to be merely the result of rapid growth, 
_when the expansion of the surface tissues does not keep pace 
with that of the inner. The effect of hot sun and dry conditions, 
y, if there is not a copious supply of water at the root, 
is to ripen growth, and this entails, amongst other things, loss 
of elasticity in the cell-walls and decrease of the power of cell- 
division. Dry conditions, whether in the case of fruits or roots, 
are felt first at the surface, and hence surface tissues are more 
subject to premature ripening. f late summer rains stimulate 
new growth, the outer, partly ripened tissues respond more 
slowly, and if the pressure from within be excessive they are 
liable to become ruptured. 
The above considerations apply to the parsnip and explain to 
a certain extent the cause of cracking. It is obvious that the 
very wet September of 1916 following the warm, dry August 
was conducive to late and rapid growth, which would, for the 
reasons given, lead to extensive cracking of the surface tissues of 
~ 
the root, and an unusual abundance of canker. In 1917 canker 
collected from various growers cracking was general in 1916 in 
parsnip-growing localities though the losses elsewhere were much 
less serious than at Evesham. One may inquire therefore as to 
the presence of special conditions at Evesham, which might tend 
probably a tendency to premature ripening. This theory receives 
support from the fact that several growers maintain that liability 
to canker is lessened by late sowing. The soil itself may be too 
rich. Though fertilizers are never applied directly to the crop, 
manured, an 
evidence, in the case of certain growers at all events, that parsnips 
are grown on the same land for two years in succession and that — 
a proper rotation is not given. The effect of the latter course 
is not only unfavourable for parsnip growth, but s to stock 
