73* 
THE TROPICAL 
AGRICULTURIST. [February i, 1882. 
fungus, and some others of less note. And it was 
while investigating the structure of the scutellum or 
cotyledon of the cereal grasses, for a purpose altogether 
apart from mycology, that I discovered that the my- 
celic sporidia of the red rust, in . its non-parasitic 
system, entered the structure of the embryo through 
the absorptive apparatus of the scutellum, mixed up 
with its albuminous food, and that these sporidia lay 
in the tissues as little sclerotic granules, in a condi- 
tion which I propose to call apogestaiion ; that is, 
gestation in living tissue, away from the generating 
species of plant, preparing to come into fruit under the 
necessary circumstances at the proper time. 
I had been vainly working at the potato fungus, 
the peronospora infestans, on some points not altogether 
eleared up by De Bary and Mr. Worthington Smith, 
on the current assumption that the infecting conidia 
were carried atmospherically, and that the mycelium 
of their zoospores, entering the stomata of the leaf, 
took a turn about there among the cells to see what 
was doing and came out again into the open air to 
produce fruit. In which assumption, I may say in 
passing, lurks the weak point that the fungus must 
have a stock of ripe fruit before it becomes a para- 
site at all — which is absolutely fatal to the theory. 
But. now, here was a new point of interrogation ; and 
in the application of it to the potato disease the results 
have been beyond anything that I anticipated. I can- 
not go into the whole subject, which has not yet 
been made public, bub may state that the stomata of 
the leaves, young tubers &c. are inoculated by the 
sporidia produced along the mycelic threads of the 
nonparasitic system of the fungus during the germin- 
ation of the potato buds under ground. The fungoid 
plasm spots can be detected in the leaf before it comes 
through the suface of the soil, and during the sea- 
son they become perfectly definite sclerotiets, which 
may be dissected out of Ihe tissue, sometimes in 
great numbers. They dissolve into streams of loose 
mycelium at the proper season and come out at the 
stomata to produce the fruit or conidia of the fungus. 
The disease for the current crop is gestating in the 
tissues of the plant from a very early stage ; and, 
although the conidia or fruits may be carried upon 
the air, they do not produce or increase the crop to 
which they belong, but only the crop of the following 
year. Some of them may immediately yield germinat- 
ing zoospores, but these do not mean any instant onslaught 
on the already destroyed leaf-tissue, having like other 
young people an education to go through. 
It occurred to me, in the course of my observations 
(all of which are vouched for by the microscopic, 
literature of mounted slides), to return to my coffee 
leaves, and try whether the principle of apogestaiion 
did not apply to the Hemileia. By stripping off little 
bits of the lower epidermis the mystery stood revealed ; 
the induction took another step. I have sent you 
very rough tracings of the fungus, not as being correct 
(such you will get elsewhere) but for the purpose of 
explaining my meaning more clearly. Figure No 1 is 
the stoma of a leaf which has not been inoculated by 
any sporidia from the non-parasitic mycelium. In 
No. 2, there are sporidia, both hyaline and becoming 
brown, lying about ge9tatingin the air-chamber of the 
stoma. Probably it is the action of the young bud-leaf 
itself which absorbs the minute plasm-granules. But 
that they are absorbed, and that they undergo a process 
of gestation within the leaf, is past any doubt (on my 
part). Stoma figure 3 shows the sporidia grown into 
a labyrinthic mass of fungoid matter called a Plas- 
modium, the "dark bodies" seen by Mr Abbay, any point 
of which is capable of germination. The procss of 
growth goes on at various rates in different cases, some 
never coming to birth, and in figure 4(a) you seethe 
Plasmodium, by reversing the epidermis grown over the 
whole stoma ; (b) shows the same mucous mass vertically 
down into the tissue. No. 5 (a) and (b) shows the germ- 
ination of the Plasmodium in the interior, as seen from 
the interior by reversing the epidermis, in plan and in 
vertical aspect. The growth is not towards the stuma, 
but away from it ; away amongst the loose cells on the 
lower side of the leaf. No. 0 (a) and (0) shows the 
fruit on the outside of the leaf growing from all points 
of the plasmodium, now mostly converted into myce- 
lium, out at the mouth of the stoma, just as in the 
potato fungus and in many other fungi. They all grow 
from what is practically a parasitic schrotium, that is a 
compact mass of fungoid plasm. Ergot is the best 
known of the non-parasitic schrotia. 
We now come to an important, point for the clear 
understanding of this subject. When once the concep- 
tion takes definite shape, it becomes obvious that afungus, 
which, at one stage of its life, is a parasite, must have a 
non-parasitic system, or must spend .apart of its cycle as 
a non-parasite ; more especially is this obvious where the 
parasite kills its host. Against the contention that 
the uredospore by direct germination infects the leaf, I 
place the question : where, then, does the first uredospore 
of the season come from ? 
Well, fig. 7 and 8 show the beginning of the non- 
parasitic stage of the Hemileia. There the fruits begin 
to germinate. Gall them spores, uredospores, sporangia, 
or conidia, they are simply a sac of granular plaem^ 
the parts of which may come out as zoospores and 
germinate into mycelic hues, or may form zoospores 
inside and there germinate, or may aggregate into a 
Plasmodium and germinate, or partly one tiling and 
partly another. But, as these conidia can germinate 
anywhere, they are independent of any host plant, and 
are thus purely non-parasitic. The non -parasitic myce- 
lium is of an entirely different character from the para- 
sitie; and the probability certainly is that the non- 
parasitic system can reproduce itself non-parasitically 
and non-fructively upon the ground, or the branches of 
trees, cr in any other situation. But you will notice that 
this non-parasitic mycelium is of two varieties. What 
is produced directly from the conidia or their zoospores 
is thin and hyaline or translucent, and it produces 
small resting spores. These resting spores, or equi- 
valent bits of plasmodium inside the crumpled conidia, 
produce a secondary or resting mycelium of a brown 
colour and torulose or jointed structure. And within 
these are produced a granular plasm and mimite 
Bporules which come partly to the outside and adhere 
loosely to the surface, or form little floats around the 
young growing lines. And it is only when, as in fig. 
8, where this mycelium, effusing a mass of mucous 
granules, flushes the young bud of the coffee plants, 
inoculating its sto nata with fungoid plasm, that the 
fungus again goes into the parasitic condition and 
after gestation attains its perfect stat-e in the produc- 
tion of fruit. 
There are many points to which I have not referred 
and on which my knowledge is defective. I am rather 
an intruder, and do not wish to poach on other men's 
preserves. But the principle of apogestaiion, by which 
the higher plant carries tl.ie germ of the lower to its 
birth and perfection, embraces a vast field with far- 
reaching philosophical implications, to which I cannot 
njw refer, and in this field, of which the Hemileia 
forms a corner, I am, peihaps, not an intruder ; and it 
is at this turn possibly that some hope of mitigation 
or cure may be found. I daresay everything has 
already been tried to destroy the fungus in some of 
iis forms. If it is already within the leaf in the very 
earliest stages of that leaf, the idea of protecting the 
leaf at a later period from an outside enemy does 
not apply The enemy is already entrenched, 
winking at you from h s borrowed ovary ; hatch- ■ 
ing the vilest treachery against the unsuspecting 
plant which is befriending him. You caunot 
eject hiin. But if jou could starve him out ; if you 
