68 THE 
GARDENERS 
CHRONICLE. 
шу 17, 1875, 
— 
THE RESTING SPORES OF THE 
POTATO FUNGUS. 
Now that these drawings illustrative of the fungus 
which causes the Potato murrain are published in the 
Gardeners Chronicle, it may be as well to explain at 
some of the terms used and the nature and 
habit of the bodies hereafter referred to, for such 
ers db may not be thoroughly acquainted WEN the 
Pm ch 
life h etd of 
the Potato fungus belongs. For that purpose refije 
must be made to fig. 9, which shows (greatly en- 
erse Section ugh the leaf of a 
Potato гай: the two great bodies at A A represent 
two minute hairs on the leaf, and at B B are seen the 
individual cells of which the leaf is constructed. When 
these hairs 
ranch to fungus 
coming out of a breathing pore of the leaf, E will be 
in comparison 
and at the expense 
of the ial of the leaf. Whe 
this thread ai 
bom ty the species just in the same way as 5 any 
rapid movemen y lasts for about half an hour, 
and (like the ааа. conidia or * 
before-mentioned) the swarm- 
ese best seen when within the swarm- 
_ spore F, where they arise from a differentiation of the 
contents, when once set free (с) they are, from the 
extreme rapidity of their movements, very difücult to 
ery respect with that pro- 
duced by thes erba and which grows, branches, 
and fruits in a precisely similar manner. 
Now ees great difficulty which has beset botanists 
been to account for the winter 
of course survive the frosts and rains of winter, but 
must ut the lea 
"X chis of o other species of Peronospora allied to 
the one which produces the Potato disease, reveals 
the fact of a third mode of reproduction. Simple- 
asexual, b 
nenduring, as are fe simple A 
swarm spores, these bodies are dense in substan 
black-brown in colour, and ретте estore with 
i р; ey are produced from the 
the antherid 
mycelium, by the contact of eridium and 
: lant. they 
баво into the sari ава there they re Ш 
res, n 
disease, are rds true ies coupe Instead of being 
transparent and u 
s here used will be better understood if 
n MN IUE iub Fe oogonium 
is analogous with a pod, the oosphere within answers 
to = ovule, and the oospore (or resting-spore) is the 
seed. The antheridium with its contents is 
Potato fangus- has el 
the fungus 
luxuriates to the greatest extent, and that if we onl 
knew the plant it most affects (probably some South 
same natural order also *commonly afflicted with 
hes same parasite, viz., the common Gro undsel; the . 
ores are said d be even more common in 
Sow Thistles than Lettu 
Be A oa it is double we shall have yet 
to look t other member of the na tural order 
сы» А find the a Н in any abun undance, 
yet, as the resting-spores of the Lettuce mould can b 
searching be found in the ora itself, so the resting. - 
spores of the Potato fungus have without doubt been 
found this year in the Potato plant. ; 
How this came about is now pretty generally 
Fic. 9.—TRANSVERSE SECTION OF A FRAGMENT OF POTATO LEAF WITH PERONOSPORA INFESTANS, 
Enl "1 disc ad 
American species of Sepe. we should then find 
plenty of resting-spores 
. ltgrows on various species 
of Solanum besides Solanum tuberosum ; it is even 
not unfrequent on the woody Nightshade of our 
hedges, and it grows upon the Tomato and other 
| 
I 
| 
| 
' . Murray exhibited some s of 
Potato leaves badly diseased before the ets 
Committee of the Royal Horticultural Society. In 
the corroded spots of these red Mr. Berkeley's sharp 
eye detected dark brown w: bodies ( 
As 
which they doubtlessly are, they were necessarily free, 
of cellulose 
Solanaceous plants. On these latter, however, it 
makes less headway than upon the Potato. As an | as the coat es them from the |. 
instance in point the allied pest of the garden Lettuce муоди But some similarly spotted leaves 
may be mentioned—P. first | had i оп to me, from 
described by Mr. Berkeley. Неге, if the resting- | of Horticulture, upon which I detected the old Potato 
spores of the parasite are wanted, they must not be | fungus, m: ithin 
_ sought for in the ce i here they are only | circular t bodies of two 
sparingly ing to the | me. 
