in Oats and Barley. 
399 
such an extent that they die and produce no ears, others — less 
severely attacked — produce a smaller number of ears than sound 
plants would do. Plants grown in an impoverished soil, such 
as would be produced by 25 years' consecutive cropping, have 
less \dtality to withstand the disease, so that not only do more 
die outright, but those which survive produce a smaller number 
of ears. Thus, I found 100 barley plants affected with smut 
produced only 152 ears, all of which were diseased; while 100 
healthy plants growing beside them, and taken indiscriminately, 
produced 260 ears. The length of the straw Avas also dimin- 
ished, for 100 blighted straws measured 5,843 centimetres, 
while 100 sound straws from contiguous plants, taken indiscrimi- 
nately, measured collectively 6,522 centimetres ; so that on an 
average each healthy straw was about three inches longer than 
those produced by smutted plants. 
This shows that smut has a more detrimental effect upon 
the vegetative system of its host -plant than even bunt has. For 
the celebrated French botanist Tillet found that 
],411 bunted wlieat plants produced 4,521 eai-s = 3'20 per plant; 
1,732 sound wlieat plants produced 5,454 ears = 3-15 „ 
while Mr. P. Nielsen and myself found that wheat plants in- 
fected with bunt produced on an average a few more ears than 
sound ones did. Moreover, smut destroys not only the grain 
but also the chaff, while bunt leaves the chaff and external coat 
of the wheat untouched. I find, however, that bunt reduces the 
length of the straw in about the same ratio as smut does. 
II. The spores of smut in farmyard manure, when applied 
to the field, will not to any appreciable extent infect oats and 
barley. 
The eminent German botanist Brefeld has asserted that the 
spores of the Ustilaginece, when placed in a proper nutritive 
medium, such as a sterilised decoction of horse-dung, will develop 
secondary spores, which, by budding like yeast-cells, multiply 
themselves until the nutritive material in the solution becomes 
exhausted. For this reason he considers that farmyard manure 
is the gi-eat means by which smut and bunt are spread. And 
he supports this theory by stating that practical farmers gene- 
rally believe that fields manured with fresh farmyard manure 
are more liable to smut and bunt than when no manure is used. 
Although this theory of Brefeld is veiy plausible, yet my 
investigations and experiments show it to be untenable as far 
as barley and oats are concerned. Fii-st, because, as will be 
shown below, the spores of U. segetum adhering to the exterior 
of the seed-corn do not to any appreciable extent cause the crop 
