Medical Officers of the Army of India.
25
IV.—Microscopic characters of the fungus on Pollinia nuda.
The mycelium is confined to very limited areas of the leaf tissue, extending
but slightly beyond the limits of the spore beds. It requires no special descrip-
tion, as it agrees in every respect with the usual characters of the mycelia of
other fungi of like kind.
A.—Uredospores.—These are round or pear-shaped bodies given off singly
from stalks, and breaking from them when ripe without any portion of the stalk
remaining adherent to them. By transmitted light they are brown, and the surface
of the epispore is beset with prominent tubercles. The beds on which these spores
occur bear also numerous capitate paraphyses which are colourless. In each
bed several teleutospores may be found. The uredospores measure, shortly
after immersion in water, on an average 21.6 X 20.2 µ, varying from an extreme
length of 24 µ to a minimum breadth of 18 µ Uredospores obtained from
Experiment I germinated freely in water, and one of these is represented in figure
12 after lying twenty-four hours in water in a growing cell. Each spore appears
to have three germinal pores on its equator, but a developed germinal tube pro-
trudes through only one, although the merest commencements or " buds " of two
others may be seen in each spore. In figure 12 such a " bud " is represented
in addition to the single developed germinal tube. The germinal tubes, which
attain lengths of 63 µ and upwards, are colourless, and contain finely granular
protoplasm, and in diameter measure from 5 to 6 µ. The empty spores still
remain brown, showing that the colour of the spore is due to the colouring of the
cell-walls. The cell-walls measure about 0.75 µ in thickness.
B.—Teleutospores.—These belong to the group of Puccinia, being two-
celled and borne singly on stalks which remain adherent to the spores when
these are scraped off their beds. The free ends of these spores are usually
rounded and slightly thickened, but sometimes they are not appreciably thickened,
and sometimes they are both thickened and bluntly pointed (figs. 4 and 5).
By transmitted light they are brown, and each cell contains a clear vesicular
space surrounded by coarsely granular matter. The epispore is studded ex-
ternally with fine tubercles, and the endospore is not separately distinguishable.
The whole length of the spore measures on an average 36 µ, the septum divid-
ing it into two almost equal divisions. The breadth at the septum is about 16µ,
and the extreme breadth of the upper cell, which is usually the broader, 18 µ .
The portions of adherent stalks attached to the spores measured usually twice
the whole length of the spore. The spores germinated immediately in water,
the upper cell usually preceding the lower in this respect. The upper promy-
celium emerges from the apex of the spore a little to one side ; the lower from a
point near the septum. The promycelia are colourless, simple long tubes, with
clear watery contents, excepting at the free ends, where they are finely granular.
Sometimes, however, the promycelium is short and curved (fig 5), and such
forms generally produce sporidia more certainly and more quickly than the long