Medical Officers of the Army of India.

73

and very frequently all these are on one side of the promycelium, i.e. in a row
one above another (Fig. 3, Plate II). This is not invariable, but usual. Each
sterigma bears a sporidium (Fig. 4, Plate II), and therefore four such are formed
by each promycelium. The sporidia are orange-red and oval, and measure from
15 X 9µ to 22 X 14µ. When all the four sporidia have been formed, the promy-
celium is almost colourless.

     When many spores are germinating in a very small quantity of water, only
those which have germinated earliest proceed to the normal development of
sporidia: those which germinate later (48 hours) usually exhibit the abnormal
process first described by Kienitz-Gerloff, and which I have elsewhere¹described
as characteristic of Caeoma Smilacis, and a Uromyces on Solidago Virgaurea;
that is to say, after the end of the promycelial tube has divided into four cells,
the cells round off and become detached (Fig. 8, Plate II). This abnormal
growth is not confined to spores of any peculiar form, for, as I have already
noted, there is only one kind of spore. I have not seen such detached cells
germinate.

     In connection with the germination of these spores I may draw attention to
another curious and interesting variation. In water cultivations I have occa-
sionally seen the condition represented in Fig. 10, plate II, in which a terminal
cell of the promycelium has developed a very long slender tube, in every respect
resembling the germ tube of a sporidium. Such growth obviously suggests the
suppression of sporidial formation.

     The sporidium germinates very quickly, after ripening (Fig. 6 c, Plate II).
The formation of secondary sporidia in water cultivations is not uncommon.

II. Æcidial stage onPyrus Pashia, Ham.

      This stage of the life history of the fungus I have already described
in the Journal of the Asiatic Society of Bengal,², in order to complete the
present paper I will describe it again. It is remarkable that this member only of
the several species of allied fruit-trees occurring in this region harbours the parasite.
I have frequently looked in vain for it on other species. Another noteworthy
feature is that, whilst in some years the Æcidium occurs abundantly, in others
it is rarely found. As the teleutospores are formed abundantly every year, this
can only be accounted for on the assumption that certain well-defined atmo-
spheric conditions must concur to enable the sporidia to attack the leaves.
In 1885 the Æcidium was very common; in 1886 it was remarkably rare; in
1887 it was again fairly abundant, though not nearly so common as in 1885; and
now, in 1889, it is again common (I was absent from India during 1888). Mr.
W. L. Dallas, Assistant Meteorological Reporter to the Government of India

¹ These Memoirs, Part IV.

²Vol. LVI, Part II, No. 3, 1887.

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