April 18, 1895. 
JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. 
345 
depends on an accnrate diagnosis of the disease. The symptoms must 
be studied and compared, and when the true nature of the disease has 
been ascertained the proper remedies can be applied ; but it is useless to 
think of remedies so long as the true nature of the disease has not been 
ascertained. Precisely the same course has to be adopted with plants 
suffering from disease, and it is our first duty to avail ourselves of every 
facility for determining the nature of the disease. Even if we suppose 
that any and every man who is engaged in the cultivation of plants has 
the primary knowledge which would enable him to decide at once 
whether the disease in question was caused by insects or by fungi, or 
whether it resulted from some error in cultivation, this would be the 
farthest step that the majority would take towards an accurate diagnosis. 
What more would be required may be gathered from some further 
remarks with which we will venture to trouble you. 
Diseases of fungoid origin may be classed in two primary groups, 
which we may call respectively endophytal, and epiphytal. The former 
are developed from within—outwards, analogous to small-pox ; the 
latter commence externally and establish themselves on the surface 
before they penetrate the tissues, analogous to some forms of skin 
disease. Most important, and most fatal are the forms of endophytal 
disease which, as we have said, are present, unseen, in the tissues of 
the plant, before they present any external appearance of their presence. 
The two most prevalent types of this kiiflf of disease are the rotting 
moulds, such as the Potato murrain, and the smut and rust fungi, such 
as bunt and mildew in corn crops, with such diseases of ornamental 
plants as the Hollyhock disease and the brand which affects the foliage 
of Sweet Williams, and others of the Pink family. There are some 
features in common, but there are other considerable divergencies in 
the life history and reproduction in these two types of moulds and 
rusts. In order to illustrate the importance which some knowledge of 
the life history should hold in the estimation of the cultivator we shall 
advert briefly to some of the phases in that of the rotting moulds, to 
which the general name of Peronospora is usually applied. 
Commencing with its simplest initial form, we find that the spore or 
conidium, produced in great numbers on every fertile thread when 
mature, is an elliptical, colourless minute body, having a thin outer 
coating of membrane, with fluid contents. These contents soon become 
granular, and at length collect at three or four centres, which condense 
and ultimately are distinctly separated from each other by the growth 
of a special envelope. Ultimately the membrane of the mother cell is 
ruptured, and the three or four smaller bodies which have been differ¬ 
entiated in its interior escape, each one furnished at one extremity with 
a pair of delicate moveable hairs, by means of wbich these little bodies, 
now termed zoospores, can swim actively in any thin film of moisture 
on which they may fall. Possibly this film may be on the leaf of a 
foster-plant. In a short time all motion ceases and the zoospores come 
to rest, the pair of delicate cilia are absorbed and a germinating thread 
is produced, the point of which seeks out and enters at one of the stomata 
of the sustaining plant. 
Having once obtained an entrance the thread grows vigorously, 
and a little mass of threads, called a mycelium, is soon developed 
within the tissues, capable of spreading itself through the plant which 
it has infected. In the next stage we discover that this mycelium has 
developed erect branched threads, which pass out through the stomata 
again into the external air—sometimes singly, sometimes in tufts. 
These are the fertile threads of the mould, which soon produce a single 
conidium at the tip of each of the branchlets, just like the original 
conidium whence the zoospores were developed. When fully matured 
each fertile thread produces a score or more of these conidia, which fall 
away when ripe, and then undergo transformation into zoospores, 
ready and active, prepared to pass through the same stages again, and 
indefinitely multiply the pest. 
This history represents the ordinary conidial fructification of the 
mould, by means of which it is passed from leaf to leaf, and from plant 
to plant, until the whole area is affected. How many of the minute 
conidia may be transported to a considerable distance by a breath of 
wind it is impossible to say, but it is known that they are capable of 
suspension in the air, and that they may be carried to any spot where 
there is sufficient moisture for the conidia to be differentiated into 
zoospores, and afterwards come to rest and germinate. This process 
takes place in the summer and autumn, but there is yet another means 
by which the pest is disseminated in the spring. 
The mycelium which flourishes within the substance of the plant 
infested is capable of producing larger globose bodies, chiefly within the 
stems, concealed from external view. These globose bodies secrete a 
thick envelope, mostly of brownish colour, and after development they 
remain in a state of rest within the stems during the winter. So that 
old stems of plants which are infested with the mould during the autumn 
conceal within themselves during the winter a large number of these 
“ resting spores.” As the old stems rot and decay the resting spores are 
set free in the spring, and then a period of activity commences. The 
contents of these globose bodies become differentiated into a considerable 
number of zoospores, which ultimately escape by a rupture of the thick 
envelope, armed with vibratile cilia, and in all respects like the zoospores 
which are developed from the conidia. These active zoospores swarm 
over the damp soil, and are carried by the spring rains into proximity 
with the young seedling leaves of the new crop of most plants, then the 
cilia are absorbed, germination commences, the delicate threads of 
mycelium enter the nearest stomata, and infection results. In this way, 
in addition to the spread of the infection from the conidia in the summer 
and autumn provision is made for an attack on seedlings in the spring. 
It will be inferred that in order to check the spread of these diseases 
the conidia must be destroyed in the autumn to prevent their extension 
to healthy plants, and the destruction of all rotten debris must be 
carried out during the winter so as to extirpate all the concealed resting 
spores, and thus prevent the infection of seedlings in the spring. Thus 
it will be seen that a knowledge of the life-history of these parasites 
will suggest the best methods to be employed in their destruction. 
Time forbids any illustration of the growth and development of the 
rust and smut fungi, so that we must rest content with the intimation 
that in a large number of these also winter spores, or resting spores, are 
produced, which remain in quietude through the winter and awaken to 
life and vigour in the spring. Perhaps the agriculturist rather than the 
horticulturist is most interested in this group of diseases, which are 
greatly addicted to the cereal grasses, although some of them attack 
garden plants. 
The other primary group of fungoid diseases, which we have called 
epiphytal, are those in which the fungus makes its appearance super¬ 
ficially on the leaves and other green parts before the internal tissues 
are affected, and attain their purpose by choking up the stomata, 
preventing transpiration, and killing the plant by suffocation. The 
mycelium of delicate vegetative threads spreads over the surface like a 
white film, or a cottony felting, which in some cases cause the leaves to 
appear as if they had been dusted with flour or chalk. This appearance 
is very familiar to you in the hedge Maple, the cultivated Pea, the Hop, 
cultivated Koses, and the well-known oidium of the Vine. In such 
cases there is no constitutional disease to be dealt with, or rather, we 
should say, no affection of the tissues. If we are successful in getting 
rid of the external pest the plant is left comparatively healthy. The 
natural inference would be that this form of disease is more amenable 
to the action of fungicides than the endophytal, and its presence may be 
detected in its earliest stages before much mischief has been done. 
Hence it is a matter of considerable importance to the cultivator that he 
should be able at once to decide for himself whether he has to deal with 
' an endophytal or an epiphytal parasite. Having this knowledge he will 
be able to apply such remedies as experience has taught him are moat 
successful with each of these forms of disease. 
It is hardly necessary to remind practical men that there are 
numerous forms of fungi which establish themselves on tissues in 
which the vitality is exhausted; on spots which have been caused 
by other agents, with which fungi have had nothing to do ; and that 
such fungi are not true parasites, but merely saprophytes. They at 
least offer no occasion for alarm. 
The conclusion to be arrived at from these desultory remarks is, the 
importance of acquiring knowledge, not so much of the names of 
species as of the life history, and especially of the methods of repro¬ 
duction, in certain important groups. No empirical methods of plant 
treatment will be more successful than empiricism with animal disease. 
There is no panacea which will cure all sorts and conditions of plant 
disease. The only universal remedy lies in the acquisition of practical 
knowledge, and to this end we have often felt the great need of some 
authoricative manual of all the more prominent of plant diseases which 
could be in the hand of all who are interested in horticulture. Such 
book would give the descriptions of the diseases, with indications of such 
remedies as had been found effective, or might be tried with some hopes 
of success. You are well aware that the Germans, for instance, are far 
ahead of us in this respect, and possess elaborate and exhaustive 
treatises on vegetable pathology, whilst the Dritish horticulturist, 
unless he is fortunate enough to be able to read German, is compelled 
to flounder along in ignorance with no other guide than hii own 
; experience. 
I If you will permit the suggestion, it seems to us that the whole sub¬ 
ject of plant disease is one of increasing interest and importance. That 
it is intimately associated with profit and loss, as you cannot forget that 
it has been with the Potato disease and the Vine mildew, and may be 
yet, not only with the growth of Grapes, if the American Vine mould 
i becomes established with us, or even with the Peach, Apple, and Pear, 
should you still consider them to be worthy of cultivation. The only 
advice that we can tender is an increased acquaintance with the life his¬ 
tory of some of the most important and typical diseases. The acquisition 
of all possible information as to the antidotes or remedies which have 
been tried and found to be successful. And lastly, an untiring effort 
to discover the tendencies and predisposing causes of diseases, remember¬ 
ing that “ prevention is better than cure,” for if there is any science in 
horticulture it should possess some power to struggle against adverse 
circumstances and devise means to circumvent the most insidious of 
foes. 
HAEDY FRUIT GARDEN. 
Outdoor rigs.—Figs can only be cultivated in favourable situa¬ 
tions, chiefly against warm south walls where abundant sunshine is 
available to develop the fruit and ripen the growths each year. The 
next most important points in cultivation are a firm, restricted, not over- 
' rich root run, and a thin disposal of the branches on the space available 
