ON THE PREVALENCE OF-GANGRENE. 
129 
perature, the effects of a very low temperature and of extreme 
heat being precisely alike; either of them, it is well known, 
causing death even when brought about by gradations. How 
much more violent, then, must be their action, when the change 
is as sudden as the difference is great; yet such fluctuations we 
have experienced continually throughout the present season, 
and to the effects of these changes must be attributed much of 
the loss which has occurred. In looking for a remedy we must 
explain that, though the symptoms are visible only in the leaves 
and branches of the plant, there cannot be a doubt of the 
effect being first felt by the roots, and it is here the pre¬ 
ventive must be applied. Any means which present as likely 
to ward off the extremes of heat or cold, or the changes spoken 
of, will be appropriate to the purpose. The fruitful cause of 
the deaths which we have noticed this season is the exposure 
of the pots in which the plants are growing to the direct rays of 
the sun, which at times have been sufficiently intense to destroy 
the vitality of the roots, and consequently of the plant. 
Another cause has been, and is, still in active operation—we 
advert to the dry cutting winds which have been so prevalent 
since March last, more in effect like the harmattan winds of the 
coast of Africa : this it is that has proved so destructive to the 
hardier plants standing in exposed situations. 
Sometimes dry gangrene is occasioned by the too rapid 
growth of a particular branch, which by absorbing the nourish¬ 
ment due to those placed next it, necessarily induces their 
decay; this, however, is not so deadly in its consequences, and 
may be checked by a diversion of the sap, either by cutting 
away entirely the overgrowth, or by pinching off the leading 
point, which will force it to throw out laterals, and thus reduce 
the branches to an equal size. It is also caused in some instances 
by the attacks of parasitical fungi and insects : these, by fixing 
themselves, the first on the roots, and the latter on the leaves 
and branches, soon reduce the plant to a state of prostration it 
seldom recovers from ; the removal of the insects is easy, but 
the fungi are frequently very difficult to eradicate: the only 
topical application likely to effect the purpose is lime-water ; if 
this fails, the speedy removal of the plant to other and better 
soil is the only remedy. 
Moist gangrene is more partial in its effects, and consequently 
less dangerous: it is chiefly confined to the leaves, flowers, and 
