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FAMILY PETROMYZONTIDAE. 
Genus Petromyzon , Linn. 
154. P. niger , Small Black Lamprey. Very common in 
many localities through northern Illinois, ascending small streams in spring 
from Lake Michigan and the rivers. 
Genus Ichthyomyzon , Gir. 
155. I. argenteus , ( Kirt .) Grd. Silvery Lamprey. Lake Michigan 
and large rivers throughout the state. 
156. I. hirudo, Grd . A single specimen in the state collection from 
the Ohio at Cairo. 
UPON PARASITIC FUNGI. 
BY T. J. BURRILL, 
( Professor of Botany and Horticulture in the Illinois Industrial University.) 
Many doubt the action of microscopic fungi in causing diseases of 
higher plants and animals. Indeed it has only been in our century, and 
mostly in the latter part of it, that botanists have distinguished these 
minute parasites as independent plants. Schleiden (1) in a work written 
about 1845 said, u I cannot regard the true Uredines, etc., ( Coniomycetes ) 
as independent plants. Meyen (2) observed the formation of Uredo maidis 
as an abnormal process of cell formation in the interior of the cells of the 
parent plant ; and, in this respect, my own observations on Elymus arena- 
rius coincide with his.” Unger (3) in 1833 sought to prove that the so-called 
fungi were changed conditions of diseased tissues ; and Fries in a classic 
work upon fungi, holds similar views. 
But the matter is not left undecided The improvements in micro- 
scopes, and in methods of tracing the life history of low organisms, have for- 
ever settled the doubts in the minds of scientific men. Nothing can be more 
satisfactory in the way of evidence, than to see with one’s own eyes the spores 
germinating, penetrating the plant tissues, find in due time producing again 
spores like the < riginal ones. This has been done again and again, and may 
be seen by any one who will take the trouble to follow, day by day, the de- 
velopment of any of the hundreds always and everywhere at hand. Their 
1. Principles of Scientific Botany, London, 1849, p. 151. 
2. Ueber die Entwickelung des Gretreidebrandes in der Mais-Pflanzen, Weig- 
mans Archiev., 1837, p. 419. 
3. Die Exantheme des Pflanzen, Wein, 1833, p. 356. 
