526 
THE GARDENING WORLD. 
April 18, 1891. 
manner late crops or catch crops (where the first have 
failed) may he forwarded by soaking them and 
drenching the trenches before sowing the seeds. 
I now pass to seeds assisted in germination by 
various agencies. Some seeds are very hard, as the 
Canna or Indian Shot, also some tree seeds of the 
Leguminosfe. I imagine many of these are aided in 
germination by passing through the gizzards of birds 
which, to some extent, remove the outer cuticle. The 
Sacred Lily of the Nile (Nelumbium) was a long time 
before it could be grown from seed, and I am told by 
Mr. John Lee that for two years they remained dormant 
in a close stove till some were filed and notched, when 
they started into growth. Many tree seeds are drawn 
by worms beneath the soil and germinate there. You 
must have seen the frequent worm-casts beneath the 
Sycamore and Ash trees on lawns ; these seeds have 
wings which help to distribute them through the winds 
and those of the Ash and Maple are also conspicuous. 
Linnams ascribes the introduction to Europe of Conyza 
coerulea from Canada to the action of the Atlantic 
winds. It is now a troublesome weed in the north of 
France ; and it is said that the soil of Spain after an 
Atlantic hurricane is often strewn with seeds from 
America. The wind is said to lift up an edible 
Lichen from the mountains of Central Asia, which at 
first is only the size of a pin’s head, but on reaching 
vapoury clouds grows to the size of a "Walnut, and 
often falls in desert spots to the great joy of the 
inhabitants. Possibly the Manna of old may be referred 
to a storm of this kind. 
( To he continued.) 
-->$<««- 
The Amateurs’ Garden. 
SEASONABLE WORK in the GARDEN. 
Stove Climbers.—Tie in the shoots of Stephanotis 
floribunda as they develop, in order to prevent them 
becoming intertwisted with one another. Rather than 
crowd the shoots of Allamanda Schottii (Hendersoni), 
a few of the superfluous ones should be cut away, and 
the rest left to hang about rather loosely. They will 
flower more freely, and look more natural than when 
tied in closely. This applies to a great many stove 
climbers making their growth at this season. Dipla- 
denias may be allowed to run up the strings near the 
glass, and afterwards tied down to the framework (what¬ 
ever it be) used in supporting them. 
Cissus discolor.— This fine-foliaged climber likes 
plenty of light, but not full sunshine, otherwise the 
leaves soon lose that rich velvety tint which is so 
characteristic of them during the early stages of growth. 
The middle partition separating two compartments of a 
house is a capital place for it, as the foliage will be 
partly shaded for the greater part of the day. A 
northern exposure with plenty of light will also prove 
favourable to the preservation of the rich tints of the 
foliage. 
Temperature of the Stove.—The night tem¬ 
perature may now ba increased to 70°, unless the 
weather out-of-doors be very cold or windy. A rise 
of 10° during the day will also be necessary, commencing 
to give air at an early period of the day. Avoid 
cold draughts by ventilating equally all along the top of 
the house. Close early to economise sun heat. 
Solanums.—Old plants should now be cut hard 
back and placed in a. warm house to cause them to 
start away freely, after which they may be inured to a 
cold frame or planted out to complete their growth and 
set a crop of fruit. If a stock of ‘young plants is 
required, then cuttings may be taken when the young 
shoots are of a suitable length. 
Cyclamens.—Keep young plants growing on in 
heat, for upon the growth that can be made in the 
early part of summer will depend the amount of bloom 
that can be obtained from them in autumn and early 
winter. Old plants as they go out of flower should 
either he thrown away, or, if intended for flowering 
another season, they may be placed in a frame, syringed, 
and kept rather close to encourage growth for a short 
time longer. 
Vines.—The earliest permanent vinery in which 
the fruit is well advanced should he examined, and 
should the borders be dry a good watering should be 
given, which will in most cases be sufficient till the 
fruit is cut. A mulching of manure may be given to 
prevent any undue evaporation from the surface. As 
the berries begin to colour it will be necessary to give air 
night and day, increasing it as they approach maturity. 
"Melons.—Those who were fortunate in dwelling 
beyond the smoke and fog radius last winter will soon 
be able to gather their earliest crop. The atmosphere 
of the house should therefore he kept drier and airy, 
not only to promote maturity, but to improve the 
flavour of the fruit. The plants must not, however, 
be kept too dry at the root if a younger and second 
crop is carried by them. 
Figs. —Almost the same statements apply to the first 
crop of Figs as in the case of Melons. In giving air, 
however, care should be taken to exclude the east winds 
which are very prevalent at this period and productive 
of harm. Late kinds will derive advantage by an 
application of liquid manure twice a day. The night 
temperature may be kept at 65° on mild nights with a 
corresponding rise by day. 
Potatos.—The planting of the main crops even in 
northern districts should be finished without further 
delay. The soil is in excellent condition, and with 
April showers and a little warmth, growth will soon 
proceed apace. 
Broccoli. —The main crop of Broccoli may now he 
sown in beds. To prevent the birds from eating the 
seed the soil may be dusted occasionally with dry soot 
and lime ; or the beds may be netted for a time or even 
threaded with black thread within a couple of inches of 
the surface. The latter is a great deterrent to sparrows. 
Borecoles of different kinds for late work may also be 
sown at this time. 
Globe Artichokes. —Blanks that were made in 
the rows during the winter may now be made good 
with offsets from the remaining plants. Fresh plan¬ 
tations may be made from the same source. Trench a 
piece of ground 2 ft. deep, manure it well, and plant 
the Artichokes in lines, and about 4 ft. apart each way, 
so as to allow space for the leaves to make good 
growth. 
Salsafy and Scorzonera.— Seeds of these may 
now be sown in lines 1 ft. apart. As the seeds are of 
some size they may be sown at a depth of 1 in. if 
necessary, to put them out of the way of birds. 
-- 
ON THE EFFECTS OF URBAN 
FOG- UPON CULTIVATED PLANTS. 
( Concluded from p. 510). 
IV. Constitution of Fogs. —During the winter, col¬ 
lections of snow from equal areas were made at 
frequent intervals, and the amount of matter precipi¬ 
tated upon it from day to day estimated. At the close 
of the February fogs the opportunity was taken to 
make scrapings from 20 square yards of the glass roofs 
of plant houses at Kew and Chelsea. The glass at both 
localities had been washed just before the commence¬ 
ment of the spell of fogs. Each yielded an almost 
identical amount of deposit, i. e. , 31 grains per square 
yard or 6 tons per square mile. 
Dr. G. H. Bailey, of the Owens College, Manchester, 
was good enough to analyse the samples and furnishes 
the following as the result of a preliminary examina¬ 
tion of that from Chelsea. “It consisted of about 
40 per cent, of mineral matter, 36 per cent, of carbon, 
and 15 per cent, of hydro-carbons. It was interesting 
to note that there ■was present also 2 to 3 per cent, of 
metallic iron in minute particles. The sulphuric acid 
present amounted to nearly 5 per cent., and the 
hydrochloric acid to 1J per cent. The presence of such 
large quantities of volatile oils explained the oleaginous 
character of the deposits which formed from London 
smoke, and it had been noticed that, especially in the 
districts of Manchester where dwelling houses were 
much crowded together (e.g., Hulme), the deposit has 
a similar character.” 
The deposits on both outdoor and greenhouse foliage 
have been from time to time collected, as well as the 
daily accumulation on a single pane of glass during 
foggy weather. The examination of these deposits is 
not yet concluded. 
V. Physiological and Microscopic WorJc. —The op¬ 
portunity has been taken to have careful drawings 
prepared, exhibiting typical cases of damage attributable 
to fog. I have now a considerable collection of examples 
from the Royal Gardens, Kew, and elsewhere. 
Large supplies of injured plant organs have been 
forthcoming and have been submitted to chemical 
analysis. These include the leaves of soft and hard- 
wooded plants, and of Orchids. Also the leaves of 
Cattleyas and Dendrobiums, and the flowers of Cattleya 
Trianrn. The results of these analyses will be valuable 
for publication when similar analyses of the uninjured 
parts have been obtained. 
The histological characters of injured tissues, as 
exhibited by the microscope, have been carefully studied 
and drawings and notes made. Many of the facts thus 
obtained are still obscure, and require experimental 
elucidation. In the case specially of Orchid flowers, 
the distribution of the stomates would seem to have a 
definite bearing on the distribution of the fog injuries. 
In both Phalaenopsis Schilleriana and Cattleya Trianre, 
for example, the sepals are much sooner and more 
easily injured than the upper petals and labellum. 
Microscopic examination shows that whilst stomates 
are frequent on the sepals of both plants, the petals 
have relatively few, comparing equal areas of surface. 
The labellum of Cattleya in many cases was found to 
he destitute of stomates. This part is usually the 
last to show actual injury. The action of the stomates 
here is probably to afford increased access of sulphurous 
acid to the part, which then directly attacks the soft, 
unprotected cells within. 
The effects of a slow current of fog, and of sulphurous 
acid, of various dilutions, upon living protoplasm, have 
been very carefully followed under the microscope. 
The procedure in both cases was identical. A slow 
current was drawn by aspiration through a specially 
devised chamber on the stage of the microscope. The 
transparent root hairs of Limnobium with their actively 
rotating protoplasm, and portions of the leaf of 
Vallisneria, were chiefly used. The effect of dense fog 
resembles very nearly that of dilute sulphurous 
acid. The rotating protoplasm is found gradually to 
swell up and invade the vacuole, its defined margin 
becoming less aud less distinct. Finally the protoplasm 
becomes granular, and breaks down entirely, the 
rotation during the process gradually slowing, ultimately 
ceasing. The whole process with fog occupies several 
hours. This line of research will be continued during 
the summer with sulphurous acid and other sub¬ 
stances. 
VI. Possible Remedial Measures. —It is too soon to 
speak of these with confidence, until a more complete 
knowledge of all the conditions of damage to vegetation 
trom this source have been obtained. Many of the 
results obtained in the physiological inquiry are still 
obscure, and it will be necessary to carry out a series of 
experiments before some of these are elucidated. Since 
October I have had opportunity of inspecting many 
collections of stove and greenhouse plants, and growers 
have most freely communicated to me any methods 
which they employ to combat the fog. The placing of 
canvas, &c., over the plant houses in foggy weather 
has in some instances mitigated the damage, the fog 
being in this way to some extent filtered. The regu¬ 
lation of the temperature has an important bearing. 
Some cultivators keep the temperature during a fog as 
low as can be done, having regard to the safety of the 
collections in the houses. Others raise the temper¬ 
ature in the hope of, to some extent, excluding the 
fog. There can be no doubt that a high temperature 
augments the damage, whilst a lower one, to some 
extent, hinders it. 
Sulphurous acid acts more violently and immediately 
in a hot than in a cool atmosphere. Again, in a long, 
dark fog, heat unnecessarily stimulates the plants, when 
(from the prevailing darkness) their transpiring capacity 
is limited. Everything should be done to tax the 
vegetative organs of a plant to the least possible extent 
when any of the vital functions are interfered with, as 
in dull, foggy weather. In this connection it is 
important to supply water to the roots with a sparing 
hand. Heat and moisture at the roots stimulate 
absorption, whilst the leaves are unable to throw off 
an excess of moisture, as they can in sunny weather. 
I know that in many establishments these precautions 
are taken and I believe with relatively beneficial 
results. The evidence on which this opinion is founded 
is derived (1) from observation of the behaviour of plants 
under different conditions of cultivation during foggy 
weather; (2) from actual experiments in which the 
special conditions were under control. 
The action of a continuous drip of moisture on foliage 
in a closed experimental chamber containing small 
quantities of sulphurous acid gas, is to mitigate the 
immediate damage so far as the leaves, thus continuously 
moistened, are concerned. 
The degree of humidity in a house, where sulphurous 
acid is present, is a matter well worthy of attention, 
and one which I have under observation. The problem 
is a complex one, and I hope to be able to communicate 
my results later. In a dry atmosphere the sulphurous 
acid, for the most part, acts as such directly on the 
living protoplasm. In a humid one it is more rapidly 
oxidised into sulphuric acid, which has an entirely 
different action, I apprehend, on vegetation, histo- 
