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Scientific Memoirs by
convenient to begin with the aecidial stage found towards the end of June, or in
July, when the host, after the setting-in of the rains, throws out its new shoots
and leaves. At this time, in certain definite localities only, although the plant
is widely distributed all over the region, these newly-developed leaves, which are
readily distinguishable from the older leaves of the previous year's growth by
their much lighter colour, and more delicate texture, may be found attacked by
an aecidium-bearing mycelium. But, although, comparatively speaking, only a
very few individuals of this widely distributed plant are thus attacked, yet when
a plant is attacked, it is often largely so. Only these new young leaves, and
sometimes the new stems bearing them, are attacked by the aecidium, and
never the older leaves or stems. When the leaf blade is attacked, conspicuous
bright yellow patches are formed, more or less irregular in shape, and varying
in size from a small point to about 2 cm. in diameter (Fig. 1, Plate 1). These
patches are, moreover, considerably thickened, and bulged, with their convexi
-ties usually towards the lower surface of the leaf. The short petioles are very
frequently attacked, the young shoots rarely. A single leaf may bear from one
to twelve patches of invasion, and if these be carefully examined when nearly
mature, minute papillæ, brownish on their summits, are seen scattered over them
both on the upper and lower surfaces, and these are the aecidia, which do not
open widely, as in the other hitherto described Cæomata, but only by a pore
through which the aecidospores are extruded in the form of small powdery
masses. A still closer examination of these patches with a lens reveals some
pellucid spots, especially on the upper surface, and these are spermogonia.
Later in the season, towards the end of September, and in October, the
aecidal form begins to disappear, although a few aecidial patches may still,
with diligent search, be found so late as the beginning of November. The
leaves which bear aecidia apparently drop off early after the aecidiospores have
been shed, for in November, although a very few ripe aecidial patches may be
found, no dried-up patches can be discovered on still adherent leaves. But
now, in October, a new phase of the fungus is revealed. On many leaves of the
same generation which bore the aecidia, but which have now become tougher
and darker green, a number of uredo-pustules may be found; and it is especially
noteworthy that those leaves which still, at this late date, exceptionally bore
aecidia, always presented many of these uredo-pustules, but at some little
distance from the aecidial area, with intervening healthy tissue. In other words,
the uredo-pustules are formed by a distinct mycelium with, as will be later
noticed, very different characters and properties. This uredo-phase of the
fungus life-history is also very much more widely distributed than the aecidial,
and is to be found almost everywhere, wherever the host grows, and not only in
certain restricted localities as in the case of the aecidial phase. At this time
when the uredo stage is beginning to show itself, the lower surfaces of the
leaves attacked exhibit a few, or a very great many, slightly paled circular area
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