On the Life-history of a Uredine on Rubia cordifolia, Linn.

(PUCCINIA COLLETTIANA, NOV. SP. )

BY

SURGEON-MAJOR A. BARCLAY, M.B.

BENGAL MEDICAL SERVICE.

     In this species we have an interesting, and experimentally proved example
of the complete exclusion of æcidial fructification. The natural history of the
fungus led me long ago to believe that it was a complete autœcious species;
but, in the absence of experimental evidence, I was obliged to disregard my
conviction, and in my descriptive list of the Uredinea of the Simla region,¹I
named it provisionally P. helvetica, Schröter, noting my hesitation whether it
was correctly so named. Since then I have found by experiment that the
species is, indeed, complete without any æcidial fructification; and it must, there-
fore, be a new species, as I can find no evidence that Schröter's P. helvetica is
a complete species.

     Although a few new shoots and leaves may be found on this host in certain
favourable localities as early as April, yet these are never found attacked in
nature. The host is not really in full vegetative activity until moist weather
sets in, from July to October, and it is then that it is attacked by this fungus.
Thereafter the plant dries up, and the persistent leaves remain for the most
part attached to the apparently dry stems throughout the winter, and until the
next period of vegetative activity recurs. These dried leaves may often be
seen bearing immense numbers of round black Puccinia pustules, frequently
with a markedly circinate arrangement, both on the upper and on the lower sur-
face of the leaf, but mostly on the upper. The petioles and stems also bear
them, the pustules here being usually elongated. The teleutospores from
these pustules do not germinate at once, but only after a period of rest, i e. not
until the following spring. In nature they do not, as a rule, germinate until
July, but I have observed them germinating in my laboratory as early as April.
This they do in the usual manner (Figs. 2 and 6, Plate I). The promycelia divide
into four strikingly regular cells, and each produces a sporidium at the end of
a long finger-like sterigma (Fig. 2, Plate I). The sporidia are oval, measuring
from 12.5 X 10µ to 14 X 8µ. They germinate at once upon becoming
detached, in the usual way (Fig. 5, Plate I).

¹Journal of the Asiatic Society of Bengal, 1889, Vol. LVIII, Part II.

²Coloured illustrations of the natural appearance of the fungus are given in the Journal of the Asiatic
Society of Bengal above referred to.