LIFE-HISTORY OF HEMILEIA VASTATRIX. 803 
area where the spores were sown, and nowhere else on the plant, 
even when the latter was subsequently kept for several weeks. 
During the same period I further made numerous isolated ex- 
periments, none of which contradicted the above conclusions. I 
need not dwell upon the agreement between these results and 
those obtained from the anatomy of the fungus, nor is it neces- 
sary to point out the analogy between the phenomena of Hemileia- 
infections and those obtained for Uredinous fungi*. The pos- 
sible reply, that I had induced special conditions within the glass 
chambers, not realized on the various check-plants, led me to 
alter the details of the experiments by using damp bell-glasses ; 
and I found that, provided every care was taken to ensure 
the absence of spores, even very damp plants did not become 
infected. 
Here, then, in the results of experiments looked at in the light 
of the anatomical facts, was proof that the act of infection con- 
sisted in the emission of something from the spore, which made 
its way into the leaf and caused the disease. The microscopical 
examination of spores and leaves proved that this “something ” 
is a germinal tube—a direct outgrowth from the spore. 
I next proceeded to inquire if any constancy is evinced in the 
periods necessary for (1) complete germination, (2) complete 
infection and the formation of the internal mycelium, (3) the 
formation of the yellow spot and “rust,” and (4) in the duration 
of the activity of the spot. 
With respect to the germination of the spore, the following 
facts have been established by numerous experiments and obser- 
vations. Germination can only occur if the spore be in contact 
with water for a sufficiently long period. If the spore has been 
completely desiccated for some time, as is the case with spores 
which have been formed at the commencement of the dry season, 
several days may be required for the successful formation of the 
germinal tubes ; but with quite fresh ripe spores, produced in the 
moist atmosphere of the south-west monsoon, the changes are 
effected much more rapidly. In from 12 to 24 hours after the 
removal of the ripe spore from its mycelium, the tubes sometimes 
commence to form, and, as arule, the whole cycle of germination 
(i. e. the formation of a complete germinal tube, the end of which 
has commenced to block up the orifice of a stoma) has been gone 
through. 
* Vide De Bary, Monatsber. d. Berl. Akad. 1565, and lit. quoted. 
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