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Scientific Memoirs by
teleutospores, though sometimes these pustules also produce many teleutospores.
They do not, however, enlarge and coalesce to form another ring.
In this condition the fungus awaits a fresh season of growth for the host
at the onset of the rainy season, when the young leaves are again attacked by a
mycelium bearing aecidia, thus completing the circle of development.
Before proceeding now to a description of the microscopic characters of the
fungus, I may mention that if a leaf bearing teleutospore beds be placed in a
moist chamber for some hours, the spore beds swell very noticeably, and become
lighter brown in colour, or even brownish yellow. This swelling is due, as will be
more particularly explained further on, to the swelling of a gelatinous sheath,
enclosing the stalks of the teleutospores, as in the case of Gymnosporangium
spores. The amount of swelling, however, in the case of this Smilax fungus
is much less than it is in Gymnosporangium, not so much because the gelatinous
sheaths themselves swell less, but because the stalks are very considerably
shorter than those of Gymnosporangium spores. This peculiar structure of the
stalks of the teleutospores is interesting in its resemblance, not only to
Gymnosporangium spores, but also to the teleutospores of Puccinia Berberidis,
Montagne, occurring on the leaves of Berberis glauca, found on the Island
Juan Fernandez, and figured by De Bary in the plate illustrating his paper
on Aecidum abietinum 1 I will recur to these resemblances later.
Microscopic characters of the Fungus.— The mycelium which bears the
uredo and teleutospores calls for no special description. It does not give
rise to any hypertrophy of the host's tissues, nor does it form haustoria. The
hyphæ contain colourless translucent matter, and are therefore difficult to
recognise (Fig. 6, Plate I).
The aecidium-bearing mycelium has, however, a very different character.
It gives rise to very marked changes in the tissues of the host (Fig 4, Plate I),
with which it comes into contact, and, as the hyphae contain orange red
globules in abundance, they are readily recognisable in fresh sections. Moreover,
the mycelium gives rise to the accumulation of nutritive material in the parenchy
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ma cells among which it ramifies. The amount of hypertrophy caused in the
leaf tissue is considerable, making the thickness of the lamina three times its
normal size when the parasite is fully developed. The effect upon the host's
tissues produced by this fungus is clearly shown in figures 4 and 5, Plate I, re
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presenting sections of the normal and attacked leaves sketched under exactly
similar conditions. In the first place it will be observed that in the normal
leaf there is no division of the subepidermal tissue into palisade and spongy cells,
all being of the latter kind. When the leaf is attacked by the aecidial para
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site, these spongy cells are greatly hypertrophied, whilst mycelial filaments per
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meate the tissue, sometimes destroying the cells but never apparently entering
them as haustoria (Fig. 7, Plate I). In the normal leaf it is also seen that the
fibrcvascular bundles usually extend through the entire depth of the lamina,
1 B o t a n i s c h e Z e i t u n g , 2 8 t h N o v e m b e r 1 8 7 9 , N o . 4 8 , p . 8 4 6 .