in Oats and Barley. 
407 
the gerininative faculty was more tliau a hundred times as great. 
This accords with the well-known fact that wheat is less liable 
to be smutted than other kinds of com. All this tends to show 
the distinctness of wheat smut from the other varieties. 
Further researches are desirable before we pronounce these 
diffei'ent kinds of smut to be true species. For the present it is 
safer to regard them as varieties, which may be thus designated : 
Wheat smut, Ustilago segetum, var. tritici. 
Oat smut, Ustilago segetum, var. avenoi. 
Naked barley smut, Ustilago segetum, var. liordei nuda. 
Covered barley smut, Ustilago segetum, var. liordei tecta. 
I would also add that some smutted ears of oats differ very 
considerably in their appearance from others, but I have not had 
the opportunity of investigating this question minutely. 
3. Now, as it has been shown that infection is due to spoi'es 
included within the husk, we cannot regard it as impossible 
that plants may now and again, in very rare instances, be 
infected from spores adhering externally to the husk in cases 
where a spore or two may chance to be very favourably placed. 
4. As the husk of barley is closely adherent to the grain 
on all sides, it is impossible to wash out the spores when once 
they have gained an entrance, while with oats it may be possible 
to a very limited extent to do this. On the other hand, by dip- 
ping oats into water charged with spores, it is quite possible, as 
the above experiment shows, that some of them may be carried 
through the fissure in the husk to the kernel ; but this is impos- 
sible with barley. It is possible that in the process of thrashing 
some of the husk of oats may become detached — and even to a 
lesser extent may this happen to barley ; and when such grains 
are sown with spores adhering externally they may produce 
diseased plants. This may be the explanation of those experi- 
ments in which some persons have asserted that they have 
produced smutted plants by dusting the seed-corn with spores 
— although it is most probable that the experimenter uncon- 
sciously employed grain already containing spores inside its 
husk from natural infection. 
C. — Prevextiox of Smut. 
Various dressings have been recommended as preventives 
against smut in barley and oats, amongst which are (1) sulphate 
of copper in solution alone, (2) solution of sulphate of copper 
with quicklime applied about twelve hours afterwards, (3) sul- 
phuric acid and water, (4) quicklime with or without subsequent 
treatment with common salt. 
