102 
A NOTE ON INDIAN WHEAT-RUSTS. 
even the space between adjacent drills, became at the same time of , 
a uniform rusty-red colour from the layer of shed uredospores that 
coated it. 
In some instances, however, and this was more particularly the case 
with the glutinous wheats, the blight seemed to affect the higher culm* 
leaves either before or at the same time as it appeared on the lower 
stem-leaves and on the tuft of leaves at the base. The early portion 
of the period — latter half of January and first half of February— to 
which our observations at Shibpur refer, was marked by those morn- 
ing river-fogs characteristic of the season in the Gangetic delta. On 
such a morning the drops of water that studded the upper surface 
of the leaf-blades, both of wheat and barley, had a tinge of orange 
imparted to them by reason of the number of uredospores held in 
suspension within them. The slight breeze that, as a rule, accom- 
panies tha lifting ** of such a river- fog is thus clearly sufficient to 
carry these spores from one plant to auother, while the moisture 
deposited on the leaves during the fog provides a means of arrest- 
ing the spores, ^^'hether the uredospores thus arrested in these 
dew drops actually did affect the wheat or not, it is certain that^ if 
they were capable ot affecting either the wheat or the barley, ample 
opportunity was afforded them of so doing. 
During the first careful conjoint survey that was made by us of 
this wheat-field, it was found that Launea asphnifolia DC., — a 
common weed in Bengal, where it bears the name tikehana^ and 
locally abundant about Shibpur— carried on the upper surface of its 
leaves in great quantities the uredospores of a Puccinia which 
seemed as if it might possibly be the one present on the wheat. In 
another part of the field it was found that malformed shoots of the 
same Launea bore what were apparently the aecidial fructifications 
of the same blight. Presently too it was discovered that the 
under-surface of the leaves of this Launea carried, in some cases, 
the teleutospores of obviously the same Puccinia. 
Minute examination having shown that it is not possible by 
structural or metric characters to differentiate the uredospores of 
the Puccinia present on the wheat from those of the Pt^ccinia pre- 
sent on Launea asplenifolia^ and having thus rendered it, under the 
circumstances, possible that the two may be specifically identical, it 
became necessary to undertake experimental cultures in order to 
confirm or to disprove their identity. Ihe lateness of the sowings 
and consequent lateness of appearance of the rust on the wheat at 
Shibpur and of th^ discovery of this Puccinia on Launea aspleni folia 
