November 27 , 1884. ] 
JOURMAL OF HORTICULTURE AND COTTAGE GARDENER. 
479 
before the spawn threads are woven over the little organs of transpiration, 
and before the leaves are injured by the piercing of the little suckers from 
the fungus spawn. When Roses are badly mildewed tl\ey may be 
syringed where practicable with water, softsoap, and sulphur—5 gallons 
of cold water, half a pound of the best softsoap, and a handful or two of 
flowers of sulphur, the whole to be left for a few hours for the soap to 
thoroughly dissolve. Two dressings of this mixture will generally 
remove all traces of the fungus, and green fly too should it be present. 
Pure water to be afterwards used. Roses in houses could be easily reacbei 
by sulphurous fumes, but this part of the subject we leave to practical 
and experienced growers. The spores of Rose mildew very soon perish 
in the air ; they cannot withstand dryness, beat, moisture or cold ; there 
is no evidence to show that they can live for more than a day or two at 
most. Unless they light upon Roses or some allied plants they perish 
at once. We have shown that Nature has provided for this emergency 
by the constant and repeated production of vast numbers of fresh spores. 
When the chilly weather of autumn arrives the mildew has vanished ; 
Fig. 80.—Kose Mildew : its early state, enlarged 400 diameters. 
every spore of the Oidium has collapsed and perished—not a single Oidium 
spore can possibly survive the winter. How, then, does this plague of 
gardeners tide through the frosts of winter and reappear in the following 
summer? Nature protects the Oidium of Rose mildew from destruction 
in the following manner :— 
If the dying Rose leaves of autumn are examined—leaves that have 
been injured or killed by the mildew—it will be seen with a lens that the 
spawn threads are here and there dotted over with little black grains' 
Each grain is so small as to be invisible without a magnifying glass. 
Under a strong hand-glass the dots look like minute but perfectly round 
grains of gunpowder. We will now put an autumn leaf fragment under the 
microscope and magnify 100 diameters. This is only one-half the 
magnification of rig. 79 and one-quarter of fig. 80. The black dots are 
now seen as at A, fig. 81; they grow from the spawn threads of the 
Oidium or mildew. Each dot is a perfect black sphere or round box 
furnished with radiating brown tentacles or appendages as shown. The 
use of the appendages to the fungus is uncertain. As each little black 
globular box is not larger than the point of a needle it may be considered 
by some as no easy matter to cut one in two and see the nature of the 
inside. Still, the performance of this feat is quite possible. If many sections 
are taken with a lancet or razor one or more of these boxes will bo seen in 
section. Su( h a section is shown at B. It will be noticed that there is a 
comparatively thick outer coat to the box, made up of minute pieces spliced 
or dovetailed together. This outer coat, inconceivably fine and thin as it 
is, is droughtproof, frostproof, and waterproof. Dryness, coldness, or 
wetness will not injure it or its contents. Within the box, and repre¬ 
sented by a single fine line in the section, is a small, transparent, globular 
llidder, and inside this bladder there are eight neatly and cosily packed oval 
spares or seeds of mildew. Nature takes such extreme care for the preser¬ 
vation of her smallest works that she takes all these pains to preserve the 
spores—always eight in one bladder, each bladder in a circular air-proof 
black box, and all invisible to us without the microscope. The box is 
termed by botanists a perithecium or conceptacle, or one box which covers 
another, and the bladder inside is termed an ascus, meaning a sack, 
bladder, or bottle. 
The whole apparatus is so neatly and well made and so perfect that the 
frosts, rains, and winds of winter have no effect whatever on the eight 
little mildew spores so snugly packed away. One infected Rose leaf will 
bear hundreds of these microscopic boxes, each with its bladder inside 
containing eight spores. This state of the fungus of Rose mildew is the 
perfect and most complete state ; ibis is the condition named by botanists 
Sphaerotheca pannosa. Lev. Sphserotheca means a round box or case ; 
pannosa, we presume, indicates the shrivelling effect of the fungus on the 
leaves. 
If infected Rose leaves are placed on a garden bed in late autumn they 
may he examined at different times during the winter, and the minute 
black mildew boxes will always be found uninjured by the vicissitudes 
of weather. The Rose leaves will gradually fall into decay, but the 
mildew boxes or perithecia will not decay. 
When the frosty weather of winter has gone and the old doubtful 
weather of early spring has passed away, when the warm sun of early summer 
begins to shine. Nature prepares to set 
free the spores of Rose mildew. If we 
take from our garden bed a decayed 
leaf fragment on which the boxes or 
perithecia have been borne, and ex¬ 
amine it under the microscope in the 
month of May, we shall probably see it, 
if enlarged 500 diameters, as shown in 
Fig. 82. The warm sun and warm 
showers of early summer cause the box 
to split as illustrated at A ; the bladder 
containing the eight neatly packed 
spores or seeds is then expelled through 
the opening of the box, as seen at b. 
The thin transparent bladder or ascus 
sails through the air with its tiny load 
and soon splits either at the side or top 
as at c, and the eight living spores @r 
seeds of Rose mildew, after six months’ 
rest inside, at length sail out. They 
often germinate as they float about in 
the air, and such spores as fall on to X - 100- 
Rose tres weave a web of mycelium or Fig. 8l.-Eose Mildew: its autumnal and 
spawn, and cause the immediate pro- winter state, enlarged lOO diameters, 
duction of Rose mildew in the club, 
necklace, or Oidium form first described. 
A single germinating spore, enlarged to 1000 diameters is shown at D. 
It is obvious from this description that the fungus of Rose mildew is 
preserved during the winter on decaying Rose foliage, that for every in¬ 
fected Rose leaf that is burnt at least one hundred living spores or seeds 
will be destroyed at the same time. It is, however, impossible to destroy 
or deeply bury all infected leaves ; hut, nevertheless, the more dtcaying 
Fig. 82.—Rose Mildew : its ultimate condition, enlarged 500 and 1000 diameters. 
material that is either burnt or deeply burled the less spores there must be 
to invade Roses in the spring. 
If all gardeners would agree to one course of clear-headed action the 
effects of many ailments of plants like Rose mildew would be materially 
lessened. But if one gardener is intelligent and industrious and another 
