69 
richly covered with germinating conidia, did not show a single penetra¬ 
tion spot. 
The experiments with corn and corn smut were carried on still more 
comprehensively. Infections in the heart were first made on young 
plants about 6 inches high and showing an open apex, up to those 
of more than 2 feet in height. The appearances of penetrations were 
uniformly observed in all parts of the young leaves and young axes, in 
just the same manner except that on account of the size of the corn plants 
they were yet more distinct than in the sorghum. All the young leaves 
of the bud, and the still short and unexpanded parts of the axis lying 
between, were susceptible to penetration, as well as the tips of the 
axes with the staminate panicles, when the latter were reached by the 
spraying of the infective fluid. The penetrations also ceased here only 
when all parts of the bud passed from immaturity to full development. 
■Concerning the adventive roots, and also the side sprouts of the pistil¬ 
late spikes, which appear later and were infected in the bud, I can assert 
exactly the same thing as for the buds of the main axis ; and, finally, I 
will state merely for sake of completeness, that also the scattering young 
hairs on the leaves, which are incipient in the very young leaves, are 
readily attacked by the fungous germs. Penetration spots were to be 
seen on these with especial distinctness. 
After all possible places of attack by the smut germs have been dis¬ 
covered, there nowremains to be added the results which were obtained 
in the subsequent production of smut upon the proper host plants with 
the specified smut fungi, by means of the various sorts of infection. 
This is done for the purpose of arriving at such conclusions as may be 
drawn with scientific authority in regard to the susceptibility of the 
host plants used in our experiments to smut diseases at different ages 
and stages of development, and on the appearance and spread of such 
diseases. 
A. I begin with TJstilago carbo , the notorious dusty smut which de¬ 
stroys the fruit of oats, barley, wheat, etc. The smut spores germinate 
easily and produce sprout conidia in endless generations in nutrient so¬ 
lutions. In mass, the sprout conidia have a hyaline appearance. Their 
membranes become a little slimy on the outside, so that the germs can 
not lie together closely, but often form loosely connected heaps, which 
•can again be easily dispersed in fluids. 
The infections by dusty smut ( Flugbrand) were carried on with barley 
and oats at the same time, and altogether considerably over one hun¬ 
dred series of experiments were made. In order to exclude sources of 
error, sowings of the uninfected grains were made for comparison, 
concerning which I will state, in brief, that they brought forth sound 
culms and fruit, only showing one smutty plant in two cases. 
I. For the first series of experiments the grains were chosen particu¬ 
larly in the earliest stage of germination, where tbe rootlets had already 
come forth and the plumule was just visible. The tiny plants were 
placed upon the earth uncovered and were sprinkled all over with sprout 
