Sept. 27th, 1884. 
THE GARDENING WORLD, 
61 
they should be put into heat, near the glass, and be 
kept moist at the roots, to induce young growth from 
which to propagate sufficient plants wherewith to 
furnish early in summer the number of beds allotted to 
it in the flower garden. Tom Thumb Ageratum—which 
should be in every flower garden —for the same reason 
as given above, should also be similarly treated. 
The colour—a beautiful grey—of this excellent 
Ageratum contrasts very effectively with masses of 
blue, pink, soarlet, yellow and white, when judiciously 
arranged.— H. W. 
— ~ - s — 
ROUGH-SKINNED POTATOS, 
There is extant, and pretty largely believed in, a 
popular error that only rough-skinned Potatos are 
good eating. Those who know more about Potatos 
than ordinary consumers of them do, can tell us that 
some of the most delicious eating kinds in cultivation 
have skins of the cleanest and smoothest; whilst 
the exceptions are scab and cracking in Potatos, 
supposed to be caused by some unsuitable substance 
in the soil, such as lime rubbish,”_&c. Now, it must 
be regarded, having reference to the present scientific 
tendency to charge upon fungi of some kind all 
sorts and conditions of vegetable ills, as specially 
kind of fungologists that they do not credit fungi 
with being the cause of scab. Happily that at 
least is supposed to arise from some other cause. 
But whether the inference we have quoted is that of 
the writer of the book or of the reviewer we cannot 
say, but in any case it shows deplorable scientific 
ignorance when it is stated that scab arises from some 
unsuitable substance in the soil, and we would advise 
in discussing such matters counsel should first be 
taken with some practical men. The fact that scab 
and cracking and exceeding roughness of skin is this 
year almost everywhere so prevalent shows that it is 
not produced by any unsuitable substance in the soil, 
but is the product of unusual drought and heat ; 
whilst when these appearances on the tubers are but 
length or more. Last year, curiously enough, many 
tubers were marred by sutures in them just as seen 
in Russet Apples, though the surface of the 
sutures had become coated. This year that pheno¬ 
menon is infinitesimal, whilst roughness of skin is 
universal. Many kinds that in previous seasons had 
coats as smooth and shiny as Apples now have stains 
of the roughest description. But scab seems to belong 
to a different order of eruption, and for some time 
was attributed to the attacks of earth-worms, the 
which it was supposed excoriated the skins in dry 
weather in search of moisture. Still there remained 
the difficulty in connection with this suggestion that 
scab is always but skin deep, in fact, if a disease, it is 
but a skin disease. That suggestion may well go the 
way of the lime rubbish notion and be decently 
buried. Scab and drought are without doubt in con¬ 
siderable affinity, and we shall have to look for its 
origin in some internal causes in operation in the 
tubers promoted largely by heat and drought. 
Anyone who has given close attention to the newly 
some others, having usually coarse, rough skins, are 
decidedy coarse eating. It so happens that this 
present season Potatos are almost universally rough 
in the skin, the coats resembling corduroy in many 
cases. Not only the coats, but the flesh, is full of 
cracks, and scab is abundant, even where scab is 
uncommon. We thus find that roughness of exterior 
in Potatos is more an accident of culture or of season 
than of anything else ; indeed, we have often seen 
samples of the same kind grown in the southern 
districts, where there was more heat, very rough in 
skin; whilst those from the north, where the soil is 
cooler and the growth rapid and continuous, to have 
been singularly smooth and clear. Again, even in the 
south and in the same season, we have seen, even this 
year, tubers from early-planted sets rough and scabbed ; 
whilst from sets planted a month later the same sort 
has given, if smaller, at least very smooth clear¬ 
skinned tubers. 
In a review of Mr. Smith’s book on “ Plant Diseases” 
in a contemporary, we read the following :—“ All the 
diseases mentioned except three are caused by fungi; 
the partial, as is the case in some seasons, it is evident 
that some soils are much dryer and more readily 
heated than others. In any case, these appearances 
always exist most largely in dry seasons. The notion 
that lime rubbish produced scab we had thought an 
exploded one, and was surprised to find it revived with 
such authority. It should be permitted to exist no 
longer, for it is an absurdity. 
And now it will be asked, What tangible explanation 
is to be offered for these extravasations on the coats 
of Potato tubers ? The only reasonable one that 
presents itself as far as relates to cracked or rough 
skins is that during the growth of the tubers the heat 
and drought for a time arrests it and sets or hardens 
the outer article to an unusual degree. Rain showers 
falling on the foliage and heated soil suddenly pro¬ 
motes renewed growth. There is a rush of sap into 
the tubers, and the internal pressure or'force 
employed is so great that the skins are fain com¬ 
pelled to burst to admit of the compulsory expansion 
from within. In not a few cases this year tubers show 
cracks a quarter of an inch in depth and two inches in 
forming tuber has found in lifting them ere matured 
a common appearance on their coats of small whitish 
eruptions. These, it is evident, are promoted inter¬ 
nally and are either the product of gaseous com¬ 
pounds escaping from the tubers or else of starchy 
ones, but, whatever may be their original cause, 
certain it is that heat and drought assists in their 
creation, and that it is these eruptions in the young 
skins the which, as the tubers enlarge, assume the 
form of scab. Really the appearance is, if militating 
against beauty, not otherwise objectionable, as scabby 
tubers almost invariably cook well and the excres¬ 
cences are only skin deep.—A’. 
- , -■> j -- 
Isolepis gracilis.— This is a very useful plant as 
an edging, and gives such a good finish to a group of 
plants, that it ought to be more frequently employed 
than it is. It may be readily increased by division at 
any period of the year, but the spring is the best 
time, and any good rich soil will suit it. It must, 
however, be grown in a position where it will get 
plenty of light. We believe many people fail to grow 
it well through placing it too much in the shade, and 
in not giving it sufficient manure, 
