Medical Officers of the Army of India.
21
Experiment X.—On the 10th June, some æcidiospores from Experiment IV A
were placed upon the leaves of a few haulms, which were placed with their cut ends
under water and kept in my laboratory under a glass shade. On the 27th a few pus-
tules were found on the lower surfaces of several of these leaves. Some pustules
were light brown in colour, whilst others were very dark, almost black, the latter
being the more numerous. They were all minute and circular or linear, and
caused little or no discoloration of the tissues around them; the spores from
the light-brown sori were uredospores (one of which is represented in fig. 12),
whilst those from the dark beds were teleutospores, agreeing in every respect with
those which had produced the æcidiospores used in this experiment. In this
experiment, therefore, I had completed a whole cycle of development of this
fungus in my laboratory. Both forms of spores were placed in growing cells in
pure, water and germinated freely in 24 hours. As the teleutospores germinated
so freely, I at the same time placed some on the leaves of two seedlings raised
from seed I had collected the previous autumn. Each seedling had four leaves
(excluding the cotyledonary leaves), and upon each a few spores were placed
on the 4th July. First indications of attack were afforded on the 11th, and on
the 18th all four leaves of one seedling were affected, each bearing ripe sper-
mogonia, whilst one leaf only of the other was similarly attacked. This, therefore,
was the second generation of the aecidial fungus developed in my laboratory.
This experiment also supports the view I have taken above of the distributive
function of the teleutospores.
Experiment XI.—A few detached haulms of Pollinia were placed with their
cut ends under water. The leaves were dusted with æcidiospores obtained from
Experiment IV A on the 15th June, and then kept under a glass shade in my room.
Up to the 9th July I could not detect the extrusion of any spores, although
some of the leaves appeared to have become invaded by a mycelium ; but on
the 13th numerous small dark-brown pustules were found, which, on micro-
scopic examination, proved to consist mainly of teleutospores with a few
uredospores.
Experiment XII.—Æcidiospores from Experiment V were placed upon nine
detached single leaves which were then kept in a moist chamber ; but none of
them became affected, and they soon withered.
Experiment XIII. —Some plants of this grass were placed in three pots, and
these were then placed under the numerously affected leaves of the Strobilanthes
plant described in Experiment V, and which had throughout remained in a small
glass house outside, in order that they might become spontaneously affected by
falling æcidiospores. On the 13th July, several leaves were found with pustules
mostly containing teleutospores. But a month later I was surprised to find that
new centres of attack in large numbers had appeared on the leaves of Strobilanthes
other than those I had myself inoculated. These new points of attack could
only have resulted from the teleutospores which I had myself caused to be
produced in the leaves of Pollinia imprisoned with the Strobilanthes in the