Medical Officers of the Army of India.
43
out a usual, long tube, sometimes with short branches. This cultivation, made
on the 11th October, contained new matured spores.
The aecidium is deeply placed both in the leaf and in the petiole, and is
not bounded by any peridium, but by a layer of convoluted hyphæ (Fig. 4, Plate I).
It opens by a narrow mouth both on the upper and lower surfaces of the leaf.
The hymenium is curved and the aecidiospores are given off successively from
basidia, but the ripe spores do not remain attached to one another, forming
rows, as usual. On the contrary, as each spore ripens, it is cast off, and the
cell below, which up to this time remained in a rudimentary condition, then
grows rapidly, forming another ripe spore, and so on (Figs. 18 and 19, Plate II).
The spores are pale yellow, mostly oval, with an epispore of variable thickness,
thickened at one end, and beset with large coarse spines, which are deciduous.
When just wetted, the spores measured on an average 43.2 x 25.6pµ, varying
from 36 x 28µ to 52 x 16µ. The thickness of the epispore is usually about 4µ
and 6 to 10µ at the thickened end. These spores, like the uredospores, do not
germinate at all readily in water. In one only of the numerous cultivations I made
had a few commenced to germinate after four days. Some of these had thrown
out two small germ tubes (Fig. 11, Plate II), and some only a single one (Fig.
10, Plate II). Beyond this they never went, the germ tubes were 8µ in diameter.
The spermogonia occur plentifully both on the upper and lower surfaces of
the leaf, but more especially on the upper. They are deeply sunk below the
epidermis (Fig. 3, Plate I), and through their mouths a tuft of brittle paraphyses
protrude. They are of the usual structure, and measure when ripe, 145µ in depth
and 157µ in breadth, the paraphyses protruding about 50µ beyond the mouths.
Even in this stage, and before the inception of aecidia, the leaf tissues are greatly
hypertrophied, one measurement made showing the depth of the laminal tissue
in invaded areas to be 504µ against a normal depth of 296µ close by.
Concluding Remarks. —This completes the description of the fungus, and
it now remains to add a few remarks on its life-history, and the affinities suggest
- e d w i t h o t h e r U r e d i n e æ .
I made many attempts to reproduce the aecidial form by sowing teleuto
- s p o r e s o n t h e y o u n g n e w l y d e v e l o p e d l e a v e s a t t h e t i m e w h e n t h e a e c i d i a l
form occurs in nature, but, with one exception, these attempts failed. I
do not consider the one success sufficient in itself to establish the genetic
relationship, as the possibility of accidental, and unintentional, infection must,
in such case, be admitted, but taken with the natural history of the fungus,
the one success makes it extremely probable that we have here an autce
-cious uredine. I am inclined to attribute the negative results of all my other
experiments to the absence of some necessary external condition, which I have not
yet been able to discover, and not to the teleutosporic form being foreign to the
aecidial; and I am supported in this view on two grounds, first, because I sowed the
same teleutospores, during three years, on several other hosts which bore other
aecidia in the neighbourhood, and, vicc versâ, other teleutospores from other hosts
G 2