384 
THE COTTAGE GARDENER AND COUNTRY GENTLEMAN, September 27, 1859. 
wet, will grow them. Many of the species thrive well under 
trees, or open-growing shrubs ; whilst others are suitable for 
rockeries, especially on the shady side. 
Propagated by taking up the plants in early spring, and 
cutting them into moderately-sized divisions, replanting them 
immediately in fresh soil. 
The Woodroffs are very little known, or they would be more 
cultivated, the loliage being so beautiful and refreshing to the eye. 
The flowers also being simple, neat, and well adapted for bouquets. 
ASPIIODELUS—AsrnoDEi,, on. Kixo’s SrEAK. 
Nat. ord., Liliacese. Linn. Hexandria Monogynia. 
Genebic Chabacteb.— Corolla six-parted, spreading. Nectary 
six valves covering the germen. 
Asphodei/uS .zestivus (summer). Probably a variety of A. albus. 
2 ft. White. July. Spain. 
A. alb ITS (white). Stem naked, simple ; peduncles in a cluster, 
long as the bracts; leaves linear, keeled, smooth. 2 ft. White. 
April. S. of Europe. 
A. capillabis (hair-leaved). 4ft. Pale yellow. June. S. of 
Europe. 
A. Ceetictts (Cretan). Stem leafy, branched, naked above; 
leaves filiform, striated, toothed, rather ciliated. 2 ft. Yellow. 
June. Candia. 
A. iNTEBMEDitJS (intermediate). Stem nearly naked ; leaves 
upright, cylindrical, fistular. 2 ft. White. July. Canaries. 
A. itTTEUS (yellow). Stem leafy; leaves three-sided, striated; 
stipules very large. 3 ft. June. Sicily. 
A. EAMOStrs (branchy). Stem naked, branched; peduncles al¬ 
ternate, longer than bract; leaves ensiform, keeled, smooth. 
2 ft. White. April. S. of Europe. 
A. Sebibictts (Siberian). This is only a variety of A. luteus, 
from which it differs in having smaller and shorter bracts, a 
lower stem, with earlier and paler flowers, and more glaucous 
leaves. 2 ft. Pale yellow. May.. Siberia. 
A. Tattbictts (Taurian). Stem leafy; leaves subulate, three- 
sided, striated; bracts membranous, lanceolate, the upper 
longer than the flowers. 3 ft. White. June. Tauria. 
A. TENtriOB (slenderer). This is probably a variety of A. luteus, 
from which it differs chiefly in being smaller, having finer 
leaves, with smaller, fewer, and paler flowers. Its great dif¬ 
ference is having the upper part of the stem naked, with bracts 
as short or shorter than the peduncles. 2 ft. Yellow. July. 
Siberia. 
The species of this genus are all free to bloom, producing their 
handsome Lily-shaped flowers on stately spikes rising high above 
the foliage. The best soil for them is an open sandy loam, well 
drained. 
Propagated by taking off in autumn side-offsets, which are pro¬ 
duced freely ; each offset should have roots to it. They should 
be planted immediately in a reserve-bed till they acquire strength 
to bloom, and may then be finally planted where they are to 
bloom. 
A. intermedins is rather tender, requiring to be taken up, 
potted, and placed for shelter from frost in a cold pit. 
ASPIDISTRA LURIDA VABJEGATA. 
This is commonly an inhabitant of our stoves, yet accommodating 
itself in summer to our climate in the open air without losing 
its characteristic variegation. It has yet to be proved whether 
it will endure our climate at all seasons. T. Appleby. 
(To be continued.') 
THE SCIENCE OF GARDENING. 
(Continued from page 370.) 
THE LEAYES. 
The leaves are highly vascular organs, in which are performed 
some of the most important functions of a plant. They are very 
general, hut not absolutely necessary organs, since the branches 
sometimes perform their offices; such plants, however, as na¬ 
turally possess them are destroyed, or greatly injured by being 
deprived of them. The duration of a leaf is, in general, but for 
a year, though in some plants, they survive for twice or thrice 
that period. These organs are generally of a green colour. 
Light seems to have a powerful influence in causing this; since, if 
kept in the dark, they become of a pale yellow*, or even white 
hue, unless uncombined hydrogen is present, in which case they 
retain their verdure though light he absent. Hence their blanch¬ 
ing would seem to arise from their being unable to obtain this 
gas, under ordinary circumstances, except when light is present. 
Now, the only source from which they can obtain hydrogen is 
by decomposing water; and how light assists in the decomposition 
may perhaps be explained by the disoxygenizing power with 
which it is gifted. The violet rays of the spectrum have this 
power in the greatest degree; and Senuebior has ascertained by 
experiment that those rays have the greatest influence in pro¬ 
ducing the green colour of plants. 
Sennebier has observed that, when plants are made to vegetate 
in the dark, their blanching is much diminished by mixing a 
little hydrogen gas with the air that surrounds them. Ingen- 
liousz had already remarked that when a little hydrogen gas is 
added to the air in which plants vegetate, even in the light, it 
renders their verdure deeper ; and he seems to think, also, that 
he has proved by experiments that plants^absorb hydrogen gas 
when so circumstanced. M. Humboldt has observed that the 
To a annua and vompressa, Tlantago Xanceolata , Trifolium 
arvense, Cheiranthas cheiri. Lichen verticillatus, and several 
other plants which grow in the galleries of mines, retain their 
green colour even in the dark, and that in these cases the air 
around them contains a quantity of hydrogen gas. This phi¬ 
losopher concludes, from his observations, that t£e white colour 
of blanched plants is occasioned by their retaining an unusual 
proportion of oxygen, and that this is prevented by surrounding 
them with hydrogen gas. This may, perhaps, be true in certain 
cases ; but the expei-imcnts of Mr. Gough are sufficient to prove 
that the retention of oxygen is not the only difference between 
green and blanched plants. 
The green colouring matter of plants has been shown by 
Rouelle to bo of a resinous nature. From this, and from the 
circumstance of its being formed only in the light, Berthollet 
has inferred that the leaves of plants have the property of de¬ 
composing water as well as carbonic acid when exposed to the 
light of the sun. The oxygen emitted, according to him, is 
derived partly from the decomposed carbonic acid, and partly 
from the water, while the carbon and hydrogen enter into the 
composition of the inflammable parts of the plant. This in¬ 
genious theory, though sufficiently probable, is not susceptible of 
direct proof. From the experiments of Saussure wc learn that 
when plants are made to vegetate in pure water, in atmospheres 
destitute of carbonic acid gas, the quantity of then- fixed matter 
does not increase; but when their atmospheres contain this acid 
gas the increase of weight which they receive is considerably 
greater than can be accounted for by the carbon and oxygen 
derived from the carbonic acid absorbed. Hence it is clear that 
a portion of the water must enter into their composition. It is 
more likely that the elements of this portion arrange themselves 
in a different way than that they still continue in a state of 
water. These facts certainly strengthen the hypothesis of Ber¬ 
thollet. Indeed, if we consider the great quantity of hydrogen 
contained in plants, it is difficult to conceive how they should 
obtain it, provided the water which they absorb does not con- j 
tribute to furnish it,—( Thomson’s Vegetable Chemistry.) 
When the leaves are of any other hue than green they are 
said to be coloured. This variegation is often considered to be a 
symptom either of tenderness or debility ; and it is certain, when 
the leaves of a plant become generally white, that that individual 
is seldom long-lived. Mr. Knight, however, has demonstrated 
that variegation is not a certain indication of a deficiency of 
hardihood. 
All organs exhibiting or assuming a green colour are found to 
be capable of decomposing the carbonic acid of the sap or of the 
air when exposed to the action of solar light. In this operation 
the oxygen of the acid is exhaled into the atmosphere, and its 
carbon fixed in the vegetable tissue. Whence it seems to follow 
that the green colour of the leaves is owing to tko fixation of 
carbon; for where the decomposition of carbonic acid is not 
going on the organ remains colourless. The brightness of the 
green seems to depend upon the degree of light to which the 
organ is exposed; and yet solar light is not indispensable. 
De Candolle gave the green colour to some plants of Lepidium 
sativum merely by the light of a few Argand lamps; but they 
did not give out oxygen when placed in water. 
Still the deposition of carbon caused by the action of solar light 
does not affect the membranous tissue. Still this tissue retains 
its original colour and transparency, so that it is only the 
chromule which assumes the green colour. But how does 
carbon, which is black, yield a colour which is green ? Senne- 
