IN THE TROPICS. 
33 
As is well known, it has been shown by De Bary that this is 
only the case with the lower fungi. Hitherto Hemileia has 
been counted among the Uredineæ, but whether this is 
really the case must remain very doubtful after the obser- 
vations above mentioned, for, as is well known, the hyphæ 
of the other Uredineæ possess distinct transverse walls. It 
is further to be noted that the hyphæ always remain sterile ; 
in spite of all attempts I failed to obtain any form of fructi- 
fication ; as long as the culture remained alive, it continued 
sterile, although at times small swellings appeared at the 
tips ; it is probable that these would have developed into 
spores had it been possible to keep the cultures alive longer, 
but as they were always killed through contamination with 
Bacteria and Pénicillium, I was at the most only able to 
study them for a fortnight. The spores appear only to 
germinate in presence of plenty of free oxygen, for the 
above-mentioned phenomena of germination only appeared 
in those which were swimming on the surface of the solution, 
those which were submerged all remaining unaltered. 
Although these cultivation experiments afford but little of 
interest, I have taken the opportunity of describing them, 
in order to point out that it is certain that with modern 
methods important contributions may be made to the deve- 
lopmental history of Hemileia ; the principal difficulty is 
to obtain pure cultures, and for this there are still many un- 
tried methods available ; once let the developmental history 
pf this fungus be made out, and we can then hope to find 
means of limiting the devastations of this formidable disease. 
The nutritive solution was always used in a very dilute 
form ; the best results were obtained with solutions which 
had not been heated for some months. 
Sterilization naturally plays a great part in mycological 
investigations in the tropics. In the rainy seasons almost 
everything is infested with fungi ; I have always and in all 
cases used alcohol. Brightly polished instruments were 
kept in spirit, and before use passed through a flame, and 
