406' The Propagation and Prevention of Smut 
practical farmer this information is of importance, as tliere is 
no fear of adjacent fields sown with different crops infecting one 
another : a smutted barley field, for instance, will not infect a 
field of oats, or vice versa. 
I further find, however, that there are two distinct species or 
varieties of smut which affect barley. One, the commoner, com- 
pletely destroys the entire ear, including the outer envelope of 
the kernels, so that in a week or two the spores are scattered by 
the wind, leaving the rachis bare. The affected ears emerge from 
their sheaths in the same way as healthy ears do, namely from 
the top. This I propose to call TJstilago segetum, var. nuda, 
" The naked smut." The other kind, which is less abundant in 
Denmark, does not destroy the outer case of the kernels ; this 
remains intact for some time, but eventually a certain proportion, 
of the spores escape through numerous minute fissures which 
appear in it = var. teda, " The covered smut." The affected ears 
are, moreover, at first nearly twice as broad as the healthy ears 
are, and do not, like them, emerge at the top of the sheath but 
through its sides. 
In 1886 I examined a great number of specimens of these 
two varieties and satisfied myself of their distinction. Sub- 
sequently, however, I had sent to me a few plants affected with 
both kinds (mida and tecfa), which led me to re-investigate the 
subject this year. In the experiment quoted above with barley 
smut, the variety teda only was used for infecting the bare 
kernels. The result was, that out of the 78 smutted ears thereby 
produced, two only, and these were produced on the same plant, 
were of the variety nuda. In the control plot, however, sown 
with barley which had not been artificially infected, a single 
smutted plant was produced, and this was also of the variety 
nuda. We may conclude therefore that these two plants affected 
with mala arose from a natural infection of the seed corn. Both 
kinds may usually be found in the same field, but nuda as a rule 
most abundantly. In those rare cases in which both varieties 
occur on the same plant, the explanation is simply that it has 
been naturally infected with the spores of both varieties. 
With regard to the variety of smut which occurs on wheat, 
it should be remarked that only one diseased plant was produced 
in the infection experiment quoted above. Now the germina- 
tive power of wheat-smut spores is much more feeble than of 
the other varieties. I found that of last year's wheat-smut spores 
only one or two in a thousand germinated when examined this 
year, although they had been kept in a diy place all the winter. 
Further, wheat-smut spores produced this year (1888) germinated 
even more feebly, while with barley-smut and oat-smut spores- 
