190 
JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. 
[ August S8, 188-i, 
suburbs bad nearly half as much more. The reason is not far to seek ; in 
fact, it was illustrated yesterday afternoon in the grounds of the Health 
Exhibition. While the fountains were at work, the Gluards’ band playing, 
and the sun shining brightly, a chimney connected with the machinery 
department was pouring out a dense mass of smoke, producing a strange 
combination, certainly strangest of all at a Health Exhibition which has for 
one of its foremost objects “the abatement of the smoke nuisance.” That 
canopy of black unburnt coal it is which deprives London of a third to a 
half of its bright sunshine. It is because at Kew, Apsley Guise, Marlborough, 
and Hastings there is less of this canopy that the Sunshine Eecorder tells a 
pleasanter tale of those places.” 
AERIAL ROOTS ON VINES. 
Much has been said and written at various times on the cause 
and effect of air roots on Vines. While some maintain that their 
presence is chiefly or entirely due to the proper roots being confined 
in a wet, cold, unsuitable border, others as stoutly argue that this has 
little or no influence in their production, but that excessive atmo¬ 
spheric moisture alone is the chief if not the only cause of their 
emission from the stems above the ground line. Others hold as firmly 
to the opinion that not only may both these conditions produce them, 
but that any check or injury received by underground roots will, if 
the atmosphere be suitable to the growth of the Vine, cause their 
almost immediate appearance on the stem. Having a desire to prove 
which of these theories was the correct one, I some time ago deter¬ 
mined to make a few experiments with this object in view, and after 
continued and oft-repeated careful trials which would scarcely interest 
your readers, I was compelled to conclude that excessive atmospheric 
moisture alone, especially in the early stages of growth, is the chief 
if not the only cause of their existence. 
No check nor injury to the roots, no border be it ever so cold, will 
cause their emission if the atmosphere be in that condition in respect 
to moisture which is most conducive to the healthy development of 
the branches and foliage. If, however, a slight increase of moisture 
be permanently maintained they will under such conditions the more 
rapidly break forth. When the underground roots are healthy and 
the border is in a suitable condition, aerial roots will not appear at all 
if the atmospheric moisture by day is not at any time permitted to 
exceed 60 to 80 per cent., the former amount to be allowed in bright 
and the latter in dull weather, while at night it may be allowed to 
increase to 80 or even 90 per cent. Under these conditions the Vine 
will grow vigorously, provided undue artificial heat is not resorted to. 
If, however, the moisture be permanently increased to 80 per cent, 
by day and 90 per cent, at night, aerial roots will quickly show, 
irrespective of other conditions. 
The use and effect of air roots is undoubtedly to increase the 
supply of food, while the atmospheric moisture is sufficiently great to 
permit of their existence ; but when that moisture is decreased, as it 
must necessarily beat the ripening period, thej'^ become very inactive, 
and when very numerous it is not unreasonable to infer that the lesser 
quantity of food caused by their failure as sources of supply at this 
critical period, does often cause the fruit to shank and be otherwise 
defective.—C. W. 
CHOICE ALPINE PLANTS. 
Erigeeon aubantiacum. —A new departure, and a welcome 
addition to its genus, which, prior to the introduction of this 
charming plant was made up of species and varieties having 
either white, blue, or lilac flowers, and which, in some instances, 
were wanting in merit. The present plant, however, when once 
seen will recommend itself to all interested in choice plants. It 
has many claims, for it is perfectly hardy, very dwarf, easily 
managed, and increased either by seeds or division. Beyond 
these it is adapted for either the rockery or border, and will, 
under ordinary conditions, thrive in any moderately rich vege¬ 
table soil. Should it be destined for the border, let it occupy a 
position in the front row, when its rich orange-coloured flowers 
may be seen to advantage. Considering that it rarely exceeds 
8 inches in height, and that its flowers often average 2 inches 
across, combined with its special merits above named, there 
should be no reason why it shall not figure among the most 
prominent of recent introductions. Its habit generally is that 
of the better known Aster alpinus, having oblong, somewhat 
spathulate, entire leaves, which are formed into a compact tuft. 
From these the flower stems arise, each bearing one of its hand¬ 
some blooms. These are freely produced during the summer 
months, and expand at a time when the colour is rather sparse 
in the garden, a fact which in itself supplies the want; and 
seeing that it seeds freely, it should receive every encouragement, 
and when the plants are fit dot them on the rock or in the border 
in colonies or groups. These will soon make goodly patches, 
and when seen en masse will constitute one of the most striking 
of perennial alpines. 
Ibis ibebica. —Comparatively few of us can speak with any 
degree of firmness as regards the requirements of this plant, and 
how few are destined to flower it more than once or twice in a 
lifetime ? For its successful culture the baking and drying 
process has long been prescribed. These, however, I consider 
quite as ridiculous as stewing or boiling. We all know that 
moisture is one of the chief conditions under which the majority 
of species of this genus thrive, and it must not be entirely 
disregarded. Not unfrequently does this plant become a victim 
to this strange fashion of “ drying off.” Who can wonder at 
this? Consider for a moment that in the tiny rhizome of this 
plant there is scarcely any enlargement whatever, neither is there 
any basal appendage which might form a fitting receptacle for 
sap, therefore to subject it to a neriodical drying process means 
simply destroying that, little amount of strength which it has 
gained since spring. I may also here state that no plant, or at 
least very few, is benefited by drying, provided that it does not 
deteriorate in the soil or become a victim to our winters. It is 
so perfectly hardy that no English winter ever harms it, nor 
does it deteriorate in our soils; on the contrary, it gains strength 
annually. The motive I have in view in making special allusion 
to this strictly spring-flowering plant at this time is that my 
remarks might tend to check those who believe in annually'’ 
lifting and storing them away. It is wrong, of this I am con¬ 
vinced from experience. 
Iris iberica is one of the most remarkable and interesting 
plants which Nature has bestowed, and might well be recognised 
as one of the wonders of the vegetable kingdom. It is of dwarf 
habit, with distinct, glaucous, linear, arched leaves, and produces 
its solitary gigantic flowers in May and June on slant stems 
which seldom exceed 9 inches in height. The prevailing colour 
of the sepals is satiny white, with a few dull red spots about 
the base; the petals are strangely spotted and veined in such a 
manner as to almost defy description ; indeed it is impossible to 
form any idea of its remarkable beauty without it, since so 
curious a combination of colour is rarely seen. The only soil in 
which 1 have known it to grow well, so as to almost attain luxu¬ 
riance, is the rich fibrous yellow loam of Kent and Surrey. It 
should be planted out to do any good, for I have never seen it 
cultivated well in pots, and am of opinion that it cannot be 
grown to perfection in pots. Some years since I had a bed pre¬ 
pared with rich loam as described above, the bed was fairly moist, 
and was fully exposed to the midday sun. The plants were 
miserable enough when planted, though as it afterwards proved 
the right spot had been selected. The second season after 
planting they had made such headway as to form splendid tufts, 
each of which produced from two to four of its striking flowers, 
and during that year we had scores of its flowei’s. Later on, in 
1875, it had so increased that I determined to send a specimen, 
along with a few others, to South Kensington. On the day of 
the exhibition it had eleven fully expanded flowers, with two 
more in the bud state, and was the admiration of many. The 
bed in which these were planted was not allowed to become dry ; 
and the loam being somewhat holding, though by no means reten - 
tive in character, materially assisted in keeping the plants moist. 
Thus placed it was evergreen, and endui-ed our severest winters 
with impunity. Thus there is no reason why a hardy alpine such 
as this should receive such unreasonable and gross treatment. 
This drying-off process has also been recommended for Iris 
Susiana, but happily we have instances where it has flowered for 
years undisturbed in cottage gardens, which at once dispels any 
notions to the contrary. I. iberica is a native of the high moun¬ 
tain ranges of Western Asia, and should receive every encourage¬ 
ment. Slugs are a great pest to this species, as also to I. cristata 
and other dwarf members of this genus. 
Ctananthus lobatus. —This forms a charming bit of blue 
for the rock garden during August and September, though it is 
seldom seen, unless it be in choice collections of alpines. It has 
in its favour a variety of claims. It is among the free growers, 
not rampant or weedy, but in all points holding a good position 
among choice plants. It is of prostrate habit, the flower stems 
taking a decumbent direction. These are terminated by flowers 
nearly an inch across, of purplish blue on the exterior, while the 
interior of the tube or throat is densely fringed with soft whitish 
hairs. The small fleshy leaves are of a pleasing green, and are 
deeply and irregularly lobed. It should be placed in a sunny 
position on the rockery where it can overhang some projecting 
ledge and make a good display with its bright blue flowers. It 
delights in sandy loam, to which add about one-fourth qf peat 
and leaf soil, and some sharp grit. It requires plenty of moisture 
during the growing season, and therefore should not be placed 
too high and dry. Cuttings root readily and may be had in 
abundance during the growing season. It deserves extensive 
cultivation, and is a good plant to offer in exchange, which will 
