cation, and either to impair or to destroy them, | 
long before the pollen can be formed. Another | 
alleged cause, sanctioned long ago by the dis- 
tinguished Jethro Tull, is humidity of the 
atmosphere, or the prevalence of fogs, or the 
bursting out of intense sunshine while the crop 
is in a moist condition; but this notion has been 
disproved by some carefully conducted appeals to 
experiment,—and is disproved also by the general 
fact, that smut is sometimes observable in an 
early stage of the plant’s vegetation, long before 
it has escaped from the leafy envelopes. A third 
alleged cause is excessive moistness of the soil, 
—and certainly this, though not a cause, is a 
very powerful provocative, insomuch that well- 
drained and thoroughly aerated soils are incom- 
parably freer from attacks of smut than wet ones ; 
but the disease occurs on even the driest land, 
and may often be observed as rife in the dry 
parts of a field as in the wet parts. A fourth 
alleged cause, sanctioned by such high names as 
those of Somerville, Walker, and Linnzeus, is the 
hatching and feeding of minute insects; but this 
opinion has been refuted by express and search- 
ing observation, and may be exploded also by the 
general fact that acari and aphides and other 
minute insects feed more or less on all sorts of 
plants, whether affected by smut or not, and 
almost always abound on decaying vegetable 
matter or on plants which are in a diseased or 
enfeebled condition. A fifth alleged cause is the 
abrasion of the seed-corn in the process of thrash- 
ing; but seeds thrashed in exactly the same way 
run to smut in some seasons and do not run to it 
in others,—and numerous grains of wheat of dif- 
ferent sizes have been experimentally bruised with 
a hammer previous to sowing, and have not been 
found to produce smutted plants. A sixth cause, 
alleged by Wolfius, is monstrosity of the embryo; 
but male flowers, or male parts of flowers, as well 
as female ones, are liable to smut,—and they have 
no embryo. A seventh alleged cause is deficiency 
of nourishment, occasioned by poverty of soil or 
by crowdedness of crop; but diseases closely akin 
to smut attack the fructification of some peren- 
nial plants whose roots and stems, from year to 
year, are so vigorous as to indicate the presence 
of ample nutrition. An eighth alleged cause is 
fermentation within the ears of corn, occasioned 
by natural humidity, or by excessive slowness of 
development and deficiency of evaporation ; but, 
if this were a true cause, it would account for 
the appearance of smut only after the seeds begin 
to be formed, and might be expected always to 
produce the disease in far greater extent than it 
is generally found to exist. Most other alleged 
causes either are akin to some of these eight, or 
are exceedingly fanciful, or confound smut with 
some other and widely different diseases ; and 
they, therefore, need not be named. 
The two species of fungi which produce smut, 
or whose spores constitute the fine, powdery, 
sooty-looking substance of the disease, possess a 
SMUT. 
somewhat close resemblance to each other, and 
are usually described under one general name ; 
yet, not only have they separate specific char- 
acters, but they make specifically different devel- 
opments in corn-plants, and produce essentially 
different economical effects on crops; and they, 
therefore, require to be separately studied, and 
distinctively understood. The Uredo segeiwm has 
no smell, and is the species popularly called 
dust-brand, bunt-ear, and chimney-sweeper ; and 
the Uredo fetida has a disgusting smell, and is 
the species popularly called bunt, stinking-rust, 
bladder-brand, and pepper-brand ;—or, accord- 
ing to a sort of discriminating popular nomen- 
clature, the former is smut and the latter is 
smut-ball. 
The Uredo segetwm is much more minute than 
most other coniomycetous fungi which attack 
gramineous plants; and, in particular, is not 
half the size of Uredo fetida. Its spores are so 
extremely small that not fewer than seven mil- 
lions eight hundred and forty thousand would 
be required to cover one English square inch. 
It first so injures the interior portions of the 
flowers of the plants which it attacks as to ren- 
der them abortive; it next makes the pedicels 
or little stalks of the florets swell and become 
very fleshy ; it next consumes the whole of this 
fleshy mass; and it finally comes through the 
epidermis and appears between the chafi-scales 
in the form of a black soot-like powder, and looks 
as if adhering by means of some gummy sub- 
stance to the young ear. It operates alike on 
wheat and barley and oats, and is essentially the 
same in them all; but it differs widely in aggre- 
gate coherence upon wheat and barley,—and 
differs also in the microscopic appearance of 
its spores,—but probably owes the differences 
entirely to the different action of the matrices 
in which it grows. It commonly attains matu- 
rity some weeks before the crop which it infests 
is ready for the sickle; and it then is a loose 
light powder resembling very fine lamp black, 
and is swept away and scattered by the winds,— 
so that, even when it has made great havoc upon. 
a crop, it is seldom seen to any considerable ex- 
tent at the time of harvest. It has sometimes 
been found to attack the leaves and the culms of 
corn plants ; but, in general, it attacks only the 
ear,—and this it completely destroys. It is 
comparatively rare in wheat, and does not seem 
to occur at all in rye, but is very common in 
barley, and still more so in oats. It has also 
been observed in several of the forage grasses. 
Some farmers absurdly think that a little of it 
in the barley crop is a good sign; and most re- 
gard it as far less mischievous than Uredo fetida. 
But, in so far as it exists, it is always and en- 
tirely a desolating evil; and it both escapes the 
observation of superficial observers, and eludes 
some of the common methods of preventing or 
extirpating it, by the early maturation and pro- 
fuse dispersion of its spores; and though really 
