PAPAVER
somniferum.
Diseases of the Poppy Plant.
CULTIVATION.
Diseases.
Peronospora.
58
Extracted from the Dictionary of
several instances in which fresh specimens were sown in water, germi
-nation was observed to take place, the method, curiously enough, being in
general somewhat different from any of those described by De Bary as
characteristic of the genus. The protoplasm at first became divided into
several, generally four, distinct masses, as though a formation of zoos
-pores were about to occur, but in place of this each mass gave origin to
a simple germinal tube. The latter elongated considerably, but remained
undivided, and showed no further development in water, and, owing to the
want of fresh-growing plants, experiments on their behaviour towards the
living tissues of the host could not be carried out."
"Prolonged and careful search was made for Oogonia and Oospores,
but entirely without avail, for, a though fresh leaves in every stage of the
disease and withered ones which adhered to blighted plants or had fallen
on the surrounding soil, as well as specimens of the soil itself, were care
-fully examined, in no instance could any such bodies be detected. This
absence of Oospores, however, may have been a peculiarity in the leaves
examined, or may be dependent on their development being confined to
some part or parts of the host not submitted to examination, such as the
capsules, cotyledons, first developed true leaves, &c." Dr. Ounningham
also examined specimens of the common weed (allied to the poppy and met
with throughout the plains of India) Argemone mexicana, in the hope
of detecting the Oospores of Peronospora on that plant, but in this
also he failed. "The absence of Oospores, " he adds, "in all the speci--
mens submitted to examination is remarkable, as there can be little doubt
that they must be produced, the recurrence of the disease from year
to year being otherwise almost inexplicable, as the conidia are, in
so far as observation goes, incapable of retaining their vitality when
dried, or of germination after any length of time. The possibility of
their development being confined to special parts of the host has been
already alluded to, and it is also possible that the germs of the my
-celium may be contained in the seed." This opinion was held by the late
Mr. Scott, viz., that reproduction must pass through the seed. The
only other likely method would be by the production of the Oospores on
some altogether different plant in the vicinity of the poppy fields, This
suggestion is of course at variance with the accepted life-history of the
better known PERONOSFOR Æ, but it is within the bounds of possibility
that some such migration from one host to another is specially adapted
to bridge over the period during which the poppy is off the fields. Dr.
Cunningham suggests at least a safe precaution that no diseased parts of
the plant should be left on the field from one season to another. It might
further be recommended that the Bombay system of burning the surface soil
( rábbing) might be tried as a prevention against the possible survival of
Oospores in the soil or attached to the roots of the plant.
The above detaled extract from Dr. Ounningham's valuable paper
has been given in the hope of its proving useful to persons interested in
the subject who may not have access to the Annual Report of the Sanitary
Commissioner with the Government of India (1873) in which the original
paper occurs. The life-history, so far elaborated by Dr. Ounningham,
gives the key to the natural course of future investigation by which the
concluding admission of failure made by Dr. Ounningham may be re
-moved from a subject of vast importance to Indian agriculture and an in--
valuable source of revenue to this country, namely, the failure to detect the
location of the Oospores or to discover the existence of any other arrange--
ment which could provide for the recurrence of the Opium Blight.
In summing up his views, Mr. Scott (a practical horticulturist) offers