478 
JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. 
[ Noyember 57, 1884. 
purchased this is a rather expensive item, and one grower, I am informed, 
pays 2.S. Qd. a load for old Mushroom-bed manure. In the best-managed 
establishments, however. Mushrooms are grown in addition, and that 
outlay is thus to some ex'ent reduced. It should further be added that 
both houses and frames are constructed in the most economical manner 
possible, utility and cheapness being the chief objects. 
As to the space required, some idea may be gathered from the fact that 
the punnets are about 6 inches in diameter, and I should think at a safe 
estimate a square foot of a good crop would fill two punnets of Kape, a 
lit'le more Cl ess being required. Thus a heated frame GO feet long with 
a bed 5 feet wide would yield about fifty dozen every fourteen days 
throughout the year, as the lights could be removed and the heat discon¬ 
tinued as the season advanced. Taking twenty-five crops in the year at 
the rate of l.s per dozen would give a yearly total from one frame of 
£62 10.S'. ; or to put it in aunther way, the yearly return per square yard 
of ground occupied would be over £l 10s., a quarter of an acre so cropped 
giving £l81-5 per annum. 
Although Mustard and Cress seed differ in cost to the extent of 4s.'per 
bushel, there is not much difference in the results to the grower. For in¬ 
stance, a bushel of Mustard or Rape is sufficient to sow 256 square feet of 
bed, the same quantity of Cress being sufficient for 384 square feet; but 
for the same cost as the Cres< 340 feet can be sown with Mustard. The 
ultimate results thus vary slightly, for though a somewhat hi.her price is 
obtained for the Cress, yet smaller quantities are required, and there is 
more uncertainty regarding the crop. As a guide to those intending to 
grow this salading it may be stated that a pint of Mustard seed is required 
for each 4 square feet, and the same amount of Cress for each 6 feet. 
From about 25 to 30 per cent, should be deducted from the estimated 
returns for the cost of the seed. Thu.=, to provide the five hundred dozen 
per week mentioned above between six and seven hundied bushels of 
80 'd are used yearly, at a cost of something over £400, or about one-third 
of the returns. The punnets are very cheap, but even for them, where 
such large quantities are grown, £2 or £3 per week is said to be the 
average outlay. It should 1 e stated that some growers soak the Rape 
seed in water before sowing to hasten the germination. 
Such are a few particulars concerning a very simple crop, which, if 
judiciously' managed, can evidently be made more profitable than some 
others apparently of far more importance. The prices and quantities have 
been chiefly furnished bv reliable market salesmen, and the information 
obtained from several different sour-ces agrees in the main facts. Further, 
to av'oid misleading statements as much as possible, the lowest figures 
•have been given in each case.—L. Castle. 
ROSE MILDEW. 
SPH^EROTHECA PANNOSA, LEV. 
Ik describing the fungus of Rose mildew there is little need to advert 
in detail to the external aspect of Rose trees when suffering from an 
attack of this plague. The deplorable appearance of infected trees is 
only too well known to every gardener. The leaves and stems of the tree.s 
appear to be thickly dusted over or frosted with a greyish-white powder ; 
every part of the pffant in bad cases is distorted, curled, swollen, blistered, 
and sometimes blackened ; the flower buds are often attacked, and then all 
chances of fair blooming are effectually destroyed. It is impossible to 
imagine a more melancholy sight in a flower garden than beds of Roses 
badly mildewed. 
We may not be able to point out how mildew can be prevented or 
destroyed, but we can at least clearly explain the habit and nature of the 
fungus which causes the mischief. S'cmetimes a knowledge of the habits 
of fungi gives a clue to a possible prevention or cure, but without full 
information it is obvious that any attempts to ward off disease is mere 
working in the dark. 
Opinions vary greatly amongst practical men as to whether mildew is 
fostered by a dry or humid season. Some say it is started by damp 
weather, others by dry. There can be no doubt, however, that in another 
clomly allied mildew—the mildew of Peas, Erysiphe—hot and dry 
weather greatly aids the spread of the fungus. Abundant watering will 
stop the spread of mildew amongst Peas in dry seasons. 
To understand the mildew of Roses a careful examination cf the 
fungus must be made with the microscope at different periods of the 
summer and autumn. As it is probable that many readers of this paper 
may not have a microscope, or if they have may not possess glasses of 
very high power, we will supply this possible deficiency by furnishing a 
series of illustrations traced from camera lucida reflections from Nature, 
direct from our own microscope. We are not aware of the existence of 
any similar illustrations in any English book, as Dr. Cooke in his excel¬ 
lent woik on microscopic fungi only gives two very small figures of the 
•ultimate condition of the fungus. 
In the first place, then, we will take a Rose leaf in the summer 
frosted on both sides with mildew. The mildew is generally more profuse 
on the lower surface. With a keen knife we will cut the leaf in two, and 
from one of the exposed cut edges of the leaf we will, with an extremely 
sharp knife or razor, cut off an excessively thin and tiansparent slice. 
When this long transparent thread-like slice is laid on its side on a glass 
slide we must cut a fragment from the middle, cover with a «lisc of thin 
microscopic glass, and then place under the microscope. 
If we magnify the fragment 200 diameters we shall see it as in fig. 79. 
The thickness of the R ise leaf, seen in section, is shown between the 
letters A and b. The upper suiface of the leaf is shown at A, the under 
surface at b. The upper surface is supported inside by a double series of 
sausage-shaped cells termed pallisade cells, as shown at c ; these cells 
make the upper surface of a leaf firmer than the lower surface. The 
lower surface is furnished with numerous little openings termed 
organs of transpiration, sometimes “ breathing pores,” one of these 
is shown at D. The circular bodies between the upper and lower 
surface of the leaf are the loosely packed constituent cells of which the 
leaf is built up. It will be seen that the leaf cells do not everywhere 
touch. The open spaces between are termed intercellular spaces, and it 
is the habit of the spawn of many fungi to grow in these spaces. All 
plants part with moisture in the form of fine vapour through the organs 
of transpiration. The lower surface of the leaf is almost invariably 
shown upwards in botanical drawings, made to illustrate fungi, because 
the fungi generally grow on the lower surface, and it is necessary to 
reverse the leaf to observe the habit of the fungi. 
We will now leave the little fragment of Rose leaf itself and turn to 
the fungus upon it. The first point to be noticed is the woven mass of 
greyish white mycelium or spawn upon both surfaces of the leaf, as 
shown at E and P. Under a simple lens this spawn looks like a thin 
stratum of spider’s web. The spawn, as will be seen by the illustration, 
is woven over the organs of transpiration. By this habit of growth the 
mouths of the plant are stopped, and the leaves are, as it were, suffocated. 
The spawn or mycelium is also furnished with minute suckers which hold 
on to the leaf and more or less pierce and injure the constituent cells. 
This piercing sets up decay. 
Springing from both beds of spawn on the leaf surfaces are numerous 
necklace-like clubs, each club being built up of numerous oval or sausage¬ 
shaped bodies. It will be observed that 
the club growths are much more robust on 
the softer and looser under surface of the 
leaf, as shown at G, than on the harder 
upper surface, as seen at H. This club¬ 
like growth is the early condition of Rose 
mildew, and this state of the fungus is 
known to botanists as Oi'dium leuco- 
conium, Desm. The name is derived from 
the Greek. The first word indicates the 
egg-like form of the cells of the club, and 
the second word the white colour. 
Two hundred diameters is a power 
barely sufficient to show the mildew well, 
so in fig. 80 we have shown a group of 
clubs under twice that power—viz., 400 
diameters. A perfect necklace-like club 
is shown at A, growing from the bed of 
spawn at B. A young club is shown at c, 
whilst at D a club is shown in the act of 
falling to pieces. Each oval body which 
goes to form a club is a spore or seed 
capable, upon germination, of reproducing 
mildew. The upper spores germinate 
more quickly than the basal ones. Each 
bead-like spore, bud, or seed is so slightly 
attached to its neighbour at top and 
bottom that the faintest breath separates 
them. All are so potent with life that 
they frequently germinate as they stand 
in club form ; others germinate as they 
sail through the air, as the one at E. The 
thread which is emerging from the spore 
is a thread of mycelium or spawn ready 
to invade any Rose it may fall upon. 
These spores are often technically termed 
conidia, from the Greek word indicating 
dust. The spores or seeds are sometimes 
produced in such inconceivable abundance 
in mildew, and especially so in the genus 
Oi'dium, that gardeners are often put to 
great inconvenience by merely inhaling 
the spores. The numbers of the fungus 
spores are so great on any badly infected 
Rose bush, that a row of seven figures to 
indicate millions gives no idea of their enormous numbers. This pro¬ 
fusion of spores is a provision of Nature for the safe preservation of the 
species. 
Nature seems to have determined that but few of her works shall be 
destroyed by man, especially her smaller works. If we make a still closer 
examination of an infected Rose leaf we may probably find other bodies 
growing from the mildew spawn resembling the growth shown at F. Each 
of these is a soit of swollen flask, densely packed with seeds or spores of 
another class. As maturity is reached the flask bursts as shown at G, the 
secondary spores are shot out in vast numbers, and many of them germi¬ 
nate as they sail about in the air, as shown at J. The spore-flask is tech¬ 
nically termed by botanists a pycnidium, from a Greek work which 
indicates dense packing, in reference to the closely packed spores or 
seeds. Our readers will now see that the fungus of Rose mildew has such 
enormous powers of reproduction, that when it has once made its attack 
on Roses, everything is in favour of the mildew and nothing in favour of 
the Rose and its grower. 
Judging by the effect of the fumes of sulphur on the O'l lium of the 
Vine, there can be no doubt that Rose mildew could easily be destroyed 
by sulphur it the fumes could be made to reach the fungus, and if they 
were applied in the earliest stages of the growth of the fungus—that is. 
Fig. 79.—Rose Mildew ; its early 
state, enlarged 200 diameters. 
