Von SCHRENK : TEACHING OF VEGETABLE PaTHoLocy 63 
of all the plants the wheat alone was attacked, and again that the 
stronger plants were less liable toattack. Again it was found that 
crowding helped the fungus, that moisture and warmth had the 
same effect, and that the spores could germinate in a drop of water. 
We spent a long time studying Erysiphe graminis, but I believe 
that the results amply warranted our doing so. 
One might have used other fungi, for instance the clubroot of 
the cabbage, the cotton wilt, and others, bearing in mind that rapid 
growth is desirable, for when you have to wait six months or more 
the interest is liable to wane. 
Having carried on one series such as the one described, it may 
be well to continue with as many more as one may have time for. 
Where live material of the bacterial diseases can be obtained, those 
will probably offer as satisfactory objects for study as could be 
Wished for. The effect which bacteria produce on the plant is 
usually noticeable after brief periods. Then again pure cultures 
can be made easily, and these can be subjected to various condi- 
tions, to show whether vigor of the parasite has anything to do 
with the virulency of the disease. The rusts can be used to some 
extent, particularly after several years, when one has succeeded in 
establishing barberry plants with aecidia. The species of Jelamp- 
Sera and Puccinia furnish useful material. 
The smuts are very instructive. We have one section of our 
Steenhouse devoted to these, using several grains. These are 
“overed with spores before planting and after several months the 
N€W spore crop is obtained. We have not yet tried any of the 
anthracnoses, probably because of the lack of living material, but 
they Ought to be easy to handle, as_ pure cultures can so readily 
be made and kept. One might go on at length with this phase of 
the study. This is hardly necessary now, for to the live teacher 
New points of view will present themselves from time to time. 
A word ought to be said about insects here, for they destroy 
Plants as much as fungi do. The entomologist has reigned su- 
Preme in this field hitherto, probably for the same reason that the 
“ystematic mycologist has had charge of the fungus side. The 
biting insects which injure plants by making wounds have little 
interest for the pathologist aside from the wounds made. Those 
—Msects which form galls, which mine in leaves and stems, or under 
