38
Scientific Memoirs by
superficial distribution of the intrusive elements and the permanent and wide
patency of the stomatic orifices is taken into account, it appears to be very
doubtful whether any diversion of nutritive materials takes place to any appre-
ciable extent, and whether the nutritive processes are not carried out by the
algal cells precisely as they are in the case of algæ attached to the common
external surfaces of leaves in place of, as in the present instance, being located
in what may be regarded as mere involutions of these surfaces.
When dealing with this question of parasitism and entophytism of algæ,
Klebs points out that Mycoidea parasitism affords the most striking example
of apparently true parasitism in algæ which is yet known, and during the
course of the past season I have met with a variety of the plant in which the
parasitism appears to be unequivocal. It occurs on the leaves of Cinnamomum
iners (Reinwardt), and is very abundant on the specimens of that tree in the
Botanical Garden, Calcutta. The affected leaves show conspicuous circular
black patches surrounded by narrow yellow areolæ and penetrating the entire
thickness of the lamina (Plate I, figs. 5, 6). Such patches are present in small
numbers on a large number of leaves, and now and then cover the greater part
of the surfaces. There is little or no elevation of the surface of the discoloured
patches above the general surface of the leaf, as there is in the case of com-
mon subcuticular patches of Mycoidea. The size of the patches naturally varies
greatly with age, ranging from 0.03 inch to 0.69 inch. As they increase in age
the centres of the patches become greyish, dry, and friable, and ultimately
disintegrate, giving origin to perforations penetrating the entire thickness of the
lamina and surrounded by black and yellow rings. If the black areas of the
patches be carefully examined during the hot weather or rains, they may fre-
quently be seen to present prominent specks which on the upper surface of the
patch appear reddish and on the lower one pale yellow, and by the aid of a
lens these are resolved into tufts of fertile filaments of Mycoidea with the
normal terminal zoosporangia. The filaments and zoosporangia emerging on
the lower surface of the patches do not merely differ in colour from those emerg-
-ing above, but are also considerably smaller. The difference in size and colour
of these inferior elements is indeed so striking that were they alone examined, it
would appear as though one were dealing with a new species of Mycoidea, but
on examining the filaments and zoosporangia on the upper surface it becomes at
once evident that this is not so. The filaments emerge from the surfaces of
the patches in little isolated tufts, and there is no general rupture of the epider-
mal tissue. In small, young patches the tufts are situated centrally, but as time
goes on and the patches continue to spread peripherally, they no longer appear
in the centre, but are arranged at intervals along a circular zone which gradually
passes more and more outwards. It is a curious fact that in these leaves which
are so abundantly affected by this peculiar form of Mycoidea, the common
comparatively superficial variety of the alga seems very rarely to occur save to