8

Scientific Memoirs by

VI.—On a destructive blight in Tea plants dependent on the invasion
of the tissues of the roots by the mycelium of a fungus.

     During the cold weather of the current year I was asked by Dr. King, the
Superintendent of the Royal Botanical Garden, Calcutta, to examine some
specimens of root-blight in tea which had been submitted to him for an opinion
as to the nature of the disease. A thoroughly decisive determination of certain
points in connection with the disease could only be attained by means of experi-
ments on infection of living plants which I have had no opportunity of attempt-
ing in Calcutta, and others certainly call for more extended observation than it
has yet been possible to give to them; still, as the information at present avail-
able appears to be of some economic value, it has seemed better to put it on
record at once than to wait until the observations are theoretically perfected.

     The specimens, as I obtained them, consisted of the lower parts of the
stems and the attached larger roots of the plants. The latter and the basal,
and probably subterranean, portion of the stems showed conspicuous malform-
ations. At intervals along the course of the roots there were a series of rough
swellings where the bark no longer retained its smooth surface and grey colour,
but was evidently broken up and mixed with masses of soil. Towards the
origin of the roots the swelling became continuous and was very great, extend-
ing thence over the lower end of the stems and thence gradually thinning off
and disappearing a few inches above. The texture of the swellings was friable,
and they evidently consisted of a mixture of dead disintegrating masses of
bark tissue, mixed with earth in varying proportions. On examining them
closely they presented a variegated appearance, due to the deep brown of the
dead bark tissues mingled with the brownish-grey soil. Here and there, too,
masses of a yellowish or rusty colour could be seen projecting from the general
surface, and on detaching portions of the surrounding material these were found
to be continuous with sheets and strands of similar colour diffused throughout
the looser superficial portions of the swelling. Similarly coloured areas were
also present in the deeper, denser parts of the bark and cambium, and, imme-
diately over the external surface of the wood, they were spread out so as in
many places to form an almost continuous thin layer. The colour here was in
some places much paler than more superficially, in certain cases being almost
white. On transverse section the wood was found to retain its hardness un-
altered and in most places appeared to be entirely unaffected. Here and there,
however, there were more or less wedge-shaped areas of grey discolouration,
with narrow, sinuous blackish margins separating them from the surrounding
normal pale yellow wood.

     On detaching portions of the rusty material and putting them into water