Parasitic Fungi of Illinois. 143 
traced. But little by little qualified observers have acquainted 
themselves with their existence as true species, veritable and 
distinct plants, and little by little have learned something of 
the mysteries of their life histories. Sometimes the advance in 
knowledge is gained by casual and lucky observations; but 
mostly by painstaking, systematic research, aided by all the 
appliances of the equipped laboratory and the fruitful skill of 
trained powers of manipulation and acute perception. A step 
gained is not only so much secured, but renders more possible 
other or further advance. The more becomes known, the easier 
progress is made, since that already acquired points the way 
towards new achievements. The beginning has been made, 
though this can scarcely be said to have been true until within 
very recent times. The men are now living and working who 
have made known nearly all the ascertained facts of physio- 
logical processes and results in these parasitic fungi. The 
germination of fungous spores.was not observed until within 
the present century. 
During the last part of the first half of this century 
learned discussions arose upon the specific distinction between 
the parasite and the host, and esteemed botanists held the 
view, that what was taken for the former was but a diseased 
condition of the latter —the rust of wheat, for example, was 
‘only the degraded cell-tissues of the wheat itself. Such 
difference of opinion, however, no longer exists among those 
who have possession of the information now acquired. The 
tissues of higher plants do not change by any processes of deg- 
radation or transformation into the things called fungi, neither 
do the latter originate in any other manner than as descend- 
ants of preéxisting parent forms through as rigid specific lines 
as can be traced among any animals or plants. It is known, 
too, that however much the fungus is found within the tissues 
of the host plant, 1t began its growth outside of the latter, and 
gained introduction only by forcible entrance. Spores are 
never taken up by absorption and carried by the aqueous cur- 
rents from part to part of the plant. The fungus passes 
through the tissues very much as roots pass through soil, some- 
times apparently without in any degree successful opposition, 
