May 30,1895. 
JOURNAL OF HORTICULTURE AND COTTAGE GARDENER, 
481 
I have three other houaea planted with No. 2 seeds, one of them 
of the same supply as in the affected house, and I have only had one 
plant diseased as yet; but in these houaea a few plants of No. 1 were 
put out. Nearly all of these have been diseased and destroyed. If 
Mr. Abbey could throw any additional light on this question of infection 
it would be of immense value to growers. Now would these affected 
houses be safe to plant in next year? Does the poison start only for 
the seeds, or may it remain in the soil ? 
What Mr. Abbey writes upon “dry rot ” in Potatoes is very curious. 
Last year all my early Potatoes had a disease which shrivelled up all the 
haulm. All the Potatoes were only the size of Walnuts. My foreman 
declared it was that late frost (on May 20th, I think) that caused this ; 
but to me it appeared quite different to frost-bite. A new house (not 
for Tomatoes) was built where these Potatoes grew. Some soil was 
moved for the foundation. This soil may have been used in potting up 
the No. 1 Tomato plants. Would this have infected them ? My late 
Potatoes last year, grown adjoining these diseased ones, were perfectly 
healthy.—S t. Julien Aeabin. 
In order to comprehend how infection of healthy Tomato plants is 
effected it is necessary to give a brief description of the fungus pro¬ 
ducing “ black stripe.” The Macrosporium tomati attacks the leaves, 
stems, and fruits extensively, spreading over their surfaces (internally) 
and ultimately destroys them, and the fruit is small, discoloured, or 
blackened and worthless. There is an absence of the rapid decay and 
stench so noticeable in the case of Tomato plants affected with the 
Potato disease fungus (Phytophthora infestans). At first a small greyish 
brown spot is visible on the leaves, stems, or fruit, and this extends in 
concentric rings ; these become brown, and ultimately much darker or 
black. The hyphse, threadlike branches of the mycelium, are brownish, 
somewhat curved, and septate. From these spring the conidiophores, or 
erect hyphas or outgrowth bearing the conidia, which (fruits) are oblong, 
pointed, and divided by transverse and longitudinal septa, as shown 
in the illustration (fig. 87). From these the conidia fall out when 
fully ripe, and are distributed far and wide, giving rise to the “ black 
stripe ” on the leaves, stems, or fruits of Tomato plants on which 
they fall, germinate, and push the germinal tube into the internal 
tissue. Thus the disease spreads from plant to plant during the growing 
season. 
It is said that the conidia from this form (Macrosporium tomati) 
may rest for the winter on the decayed leaves, stems, and fruits of 
Tomato plants, and on the ground. Mr. Wead of the New Hampshire 
College, United States of America, states positively that M.solani, an 
allied species, winters in the dead leaves and stems of Potato plants, and 
my experience is that M. tomati is only a form of that species. 
Mr. Arabin’s experience tends to confirm the view expressed. The 
spores of the fungus (M. solani) from the Potato plants seized on the 
Tomato plants at the root, for in the plant examined the disease had 
certainly ascended the stem. This confirms Mr. Iggulden’s view, also 
that of the foreman, who attributed the collapse of the Potato tops to 
the May frosts, as these would tend to produce that condition of the 
haulm favourable to the development of the fungus, backed by the 
damp weather following, for this fungus certainly delights in damp and 
somewhat cold weather, and which respect it differs from Potato fungus 
(Phytophthora infestans). 
Bordeaux mixture.—This is a recognised preventive of the disease, 
but to be effective must be applied when the plants are 6 inches high, 
and should be repeated at fortnightly intervals, so as to coat the 
growths as made with a thin film of the mixture. For reasons of easy 
application and less danger from use powder applications are the most 
desirable for use under glass. There are several such powders in the 
market, not advertised (as they should be) and in consequence are little 
known. I shall not say more about them for obvious reasons. 
To prepare precipitated carbonate of copper. Dissolve separately in 
warm water 1 lb. of sulphate of copper, and 1^ lb. of washing soda, 
when dissolved mix the two solutions together well, when carbonate of 
copper will be precipitated, then pour off the water and dry the copper 
carbonate—that is, the sediment. Weigh the carbonate of copper when 
dry, then take 100 times its weight of air-slaked lime, quite dry and in 
the finest possible powder, and add the copper carbonate, mix thoroughly, 
passing several times through a hair or very fine wire sieve, and after 
mixing keep in air-tight vessels in a dry place. Use with an ordinary 
sulphur duster or bellows. It is most important to begin in time. 
As regards disinfecting the soil, there is nothing better than quick¬ 
lime, about one-tenth mixed with the compost being sufiScient, or a peck 
per rod in the case of borders. The line acts promptly on any vegetable 
matter in the soil, such as partially decayed or strawy manure, which 
should not be used, either as manure or as mulching, for it forms the 
best nidus for the fungus, which is equally capable of existence, growth, 
and reproduction as a saprophyte or a parasite ; indeed it produces its 
•fruits more freely as the former than the latter, and those having it are in 
a great measure responsible, as it cannot possibly live where there is not 
organic matter, hence such substances as basic slag are far better than 
dressings of stable or farmyard manure, though there is little danger in 
that provided it be thoroughly decayed. A dry and well ventilated atmo¬ 
sphere is also of consequence in avoiding the disease, as it is damp and 
cold (relative to the subject) and organic matter that fosters the disease. 
Clean seeds and cleanly structures are also of the first importance in 
dealing with the low forms of vegetable life. 
There was not anything in Mr. Arabin’s specimen but plasma—no 
mycelial hyphae or conidiophores. This was stated in the reply to his 
letter, and, of course, puzzled him, as curl in Potatoes and black stride 
in Tomatoes have the authorities, to know how the disease was infectious. 
I also stated that the fruits affected might or might not produce the 
fungus, for no one can tell what a plasma will bring forth. Some¬ 
times nothing follows, yet the plants collapse and the fruit is worthless. 
I have expressed the view that our enemy is nothing more nor less 
than the so-called saprophyte Pleospora herbarum, its conidial condition 
being Macrosporium commune, which has several forms according to 
climatic conditions and host. Indoors, and as a parasite, the conidio¬ 
phores and condidia are long, drawn, and pointed ; outdoors, and as a 
saprophyte, the conidiophores are very short and very blunt in the 
conidial part, so much so as to appear quite distinct. This Macro¬ 
sporium is the product of the self-same mycelial hyphae, and is produced 
Fig. 87‘—Bla«k Stripe fungus (Macrosporium tomati) from Tomato plant under 
glass :— a, mycelial hyphse ; b, conidiophores; c, conidia; d, summer spores 
fallen out. 
from the spore of Pleospora herbarum, and it seldom goes further than 
curl in Potatoes and droojjing in Tomatoes. Occasionally, however, 
the curl is followed by the wholesale collapse of healthy Potato plant 
tops, and the destruction of Tomato plants and fruit by drooping, stripe, 
and blotch. 
The fungus (Macrosporium tomati) figured is as I first saw it in 
1873 at Grinkle Park, and certainly was accelerated by syringing the 
Peach trees, as in another house kept warmer and unsyringed there was 
not any disease in either the plants or fruit. Occasionally since that 
year 1 have seen the Potato top collapse disease and the Tomato rot—all 
Fig. 88.—“Black Stripe”(«) and “Blotch”(/) on Tomato, caused by 
Macrosporium tomati. 
the same thing—the conidial condition of Pleospora herbarum. Macro¬ 
sporium commune, as a saprophyte ; M. solani and M. tomati 
respectively as a parasite. 
Strangely in 1895 I received, through the Journal of Horticulture, a 
specimen Tomato fruit with both stripe and blotch (fig. 88) from 
Saltburn-by-Sea (about ten miles distant from Grinkle Park), and on 
May 25th the outgrowths of the fungus broke through the blackened 
epidermis of the blotch, appearing as a greyish or white mould—the 
Macrosporium solani or M. tomati. The mycelium is discernible around 
the edge of the blotch, it growing in concentric fashion, and slightly 
raises the margin surrounding the destroyed cells. Keeping this fruit 
under daily observation, and tiansfeiring the spores to liv ng plants, as 
well as decaying ones, an insight is got into tne characteristics of the 
fungus as a parasite and as a saprophyte, in both of which it certainly 
originates from, and ultimately developes into Pleospora herbarum. 
Possibly, however, there are two forms of this ; but whatever confusion 
exists botanically there is no mistaking Nature as revealed by the 
microscope.—G A. 
