THE COTTAGE GARDENER AND COUNTRY GENTLEMAN, September 27, 1859. 
385 
bier solved the problem as follows :—Carbon is, in strict pro¬ 
priety of speech, not a black, but a very deep blue; and vege¬ 
table tissue is not absolutely a pure white, but rather a pale 
yellow. Hence, the green is formed by the mixture of a yellow 
and blue. This explication, quoique tin peu mecanique , De 
Candolle regards as likely to be the true one. Yet we cannot 
help entertaining some doubts with regard to its validity. 
Surely the membranous tissue of many plants assuming a green 
colour has nothing in it of a yellow. But wherever we turn 
to look for an explication there is doubt; and the solution 
of the problem may be said to be a chemical puzzle. One at¬ 
tributes it to the presence of an oxide of iron; another to the 
predominance of an alkali; and neither solution is satisfactory. 
Yet plants placed in the dark do not lose their grefln colour if 
the atmosphere in which they grow contains a certain quantity 
of hydrogen or of azote. Humboldt found the leaves of Poa 
annua and Plantago lanceolata still green though growing in 
the galleries of the mines of Ereyberg. It should be recollected, 
however, that they must have been occasionally exposed to the 
light of the miners’ lamps. Leaves, bracts, calices, ovaries, are 
the organs that are most generally green: though you may find 
exceptions to the rule, both in organs which it includes and in 
organs which it excludes. The bracts of Bartsia coccinea are 
scarlet, and the embryo of the Mistletoe is green.— ( Keith's 
Lexicon.) 
The functions of the leaves appear to be a combination of those 
of the lungs and stomach of animals ; they not only modify the 
food brought to them from the roots, so as to fit it for increasing 
the size of the parent plant, but they also absorb nourishment 
from the atmosphere. The sap, after elaboration in these organs, 
differs in every plant, though, as far as experiments have been 
tried, it appears to be nearly the same in all vegetables when it 
first arrives to them. The power of a leaf to generate sap is in 
proportion to its area of surface, exposure to the light, and con¬ 
genial situation. 
Leaves throw off a very considerable quantity of water. Dr. 
Hales found that a Cabbage emitted daily nearly half its weight 
of moisture, a Sunflower, three feet high, perspired 1 lb. 14 ozs., 
and Spearmint exhales 1J times its weight in the same period. 
But of all the plants the diurnal perspiration of which has been 
ascertained, the Cornelian Cherry ( Cornus mascula) transpires 
the most; the exhalation amounting to nearly twice the weight 
of the plant in twenty-four horns. This aqueous expiration 
takes place chiefly during the day, is much promoted by heat, 
and checked by rain, or a reduction of temperature. 
On the free performance of this function of plants their 
health is dependent in a very high degree ; and we believe that 
half the epidemics to which they are subject arise from its de¬ 
rangement. That consequence of the clubbing of the roots of 
the Brassica tribe called fingers and toes arises, we consider, 
entirely from it. In the drought of summer, when the moisture 
supplied to a club-rooted Cabbage by its root does not nearly 
equal the exhalation of its foliage, to supply this deficiency the 
plant endeavours, by forming a kind of spurious bulbous root, 
to adapt itself to the contingency ; in the same manner that in 
dry situations, the fibrous roots of Phleum pratense, Alopectmts 
geniculatus , &c., acquire a tuberous form, because bulbous or 
tuberous-rooted plants, it is well known, will exist in a soil so 
deficient in moisture as to destroy all fibrous-rooted vegetables. 
Evergreens transpire less moisture than deciduous plants; 
which would lead to the expectation that they are more capable 
of living in dry situations, which, in general, is really the case. 
The matter transpired by a healthy plant is nearly pure water, 
5,000 grains of it never containing more than one grain of solid 
matter, and this is constituted of resinous and gummy matter, 
with carbonate and sulphate of lime. It appears to be nearly 
the same in all plants. The quantity, however, varies in every 
species, probably in every individual—and is greatly influenced 
by the quantity of water applied to the roots. Under precisely 
similar circumstances Sennebier obtained the following results :— 
Grs. Grs. 
A Peach branch, imbibing 100 exhaled 35 
„ „ 210 „ 90 
„ „ 220 „ 120 
„ „ 710 ,, 295 
"We have found the branch of a Pelargonium, that, whilst 
growing on the parent stem, exhaled only twenty grains in twenty- 
four hours, more than trebled that quantity, in the same time 
when cut from the stem, and placed with the divided end in 
water. This increased transpiration is attended by a propor¬ 
tionate reduction of temperature; for a collection of Pelar¬ 
goniums, in the midst of which Eahrcnheit’s thermometer stood 
at 55°, fell to 48° within two horns after a plentiful watering to 
their roots only, though the water was of the same temperature 
as the greenhouse. 
Eor the purpose of ascertaining the composition of the liquid 
transpired by plants, M. Sennebier collected 13,030 grains of it 
from a Vine during the months of May and June. When evapo¬ 
rated 2 grains of residuum were left, composed of nearly J grain 
of carbonate of lime (chalk), l- 12 th grain of sulphate of lime 
(gypsum), 3 grain of matter apparently gum, and | grain ap¬ 
parently resinous. He analysed 60,768 grains of a similar liquid 
collected from the Vine during July and August. The residuum 
after evaporation weighed 2 ) grains, composed of J grain of car¬ 
bonate of lime, i grain of sulphate of lime, 3 grain of gum, and 
3 grain of resin. The liquid transpired by Aster Novce-Anglice 
afforded precisely the same ingredients.— (Bncyc. Meth. Phys. 
Veget., 287.) 
As the season of growth advances the transpiring power of 
leaves decreases. Under similar circumstances Sennebier found 
the transpiration much greater in May than in September. 
The transpiration of plants decreases with that of the tem¬ 
perature to which they are exposed, as well as with the period 
of theh growth. This explains why the gardener finds that his 
plants do not require so much water in cold weather, nor during 
the time that elapses between the fall of then - blossom and the 
ripening of their seed. During this period they do not transpire 
more than one-half so much as during the period preceding and 
attending upon their blooming. 
The transpiration takes place from the upper surfaces of the 
leaves ; and, if these surfaces are coated with varnish, the leaves 
gradually decay and fall, and the growth of the plant ceases 
until fresh leaves are produced. Hence arises the benefit which 
plants derive in rooms, greenhouses, and other confined en¬ 
closures, from keeping those surfaces cleansed with the sponge 
and syringe. Some plants are particularly sensitive to injury 
from any check to tlieh transpiration, among which are the Tea- 
scented Roses ; and it thence arises that they cannot now be 
cultivated in nursery gardens near London, where they once 
flourished when that metropolis was less extensive. The advantage 
derived by plants from having then’ leaves cleansed was exem¬ 
plified by the following experiment:— 
Two Orange trees, weighing respectively 18 ozs. and 20 ozs., 
were allowed to vegetate without their leaves being cleansed for 
a whole twelvemonth ; and two others, weigliing 19 ozs. and 
20 J ozs. each, had their leaves sponged with tepid water once a 
week; the two first increased in weight less than half an ounce 
each; whilst of the two latter, one had increased two, and the 
other nearly three ounces. In all other respects they had been 
treated similarly. 
It must be remembered, however, in using the sponge and the 
syringe, that the under Bide of the leaves is an absorbing surface, 
benefited by being kept clean, and by the application of moisture. 
The Kidney Bean, Sunflower, Cabbage, and Spinach, absorb 
moisture equally by then’ under and upper surfaces ; the Cocks¬ 
comb, purple-leaved Amaranth, Heliotrope, Lilac, and Balm, 
absorb most freely by their upper surfaces; and the Vine, Pear, 
Cherry, Apricot, Walnut, Mulberry, and Rose, absorb most by 
their under surfaces.—J. 
(To be continued.) 
Death oe Peoeessob Heneeey. —Professor Henfrey, a Eellow 
of the Royal and Linnsean Societies, a Member of the Council of 
the Horticultural Society, Professor of Botany in King’s College, 
London, and Examiner in Natural Science to the Royal Military 
Academy and the Society of Arts, died at his house at Turnham 
Green on the morning of the 7th inst. Professor Henfrey has 
long been known as an excellent histologist and sound vegetable 
physiologist. Especially conversant with the botanical literature 
of the Germans, we owe to his pen many valuable dissertations 
upon subjects little attended to in England. The papers in the 
“Micographic Dictionary,” written by him in conjunction with 
Dr. Griffith, are celebrated for then’ accuracy as well as skilful 
condensation. The physiological part of his “Elementary Course 
of Botany,” and the papers on “Vegetable Structure,” nowin 
course of publication in the Journal of the Royal Agricultural 
Society, will always be regarded as the productions of a man 
not only familiar with the truths of science, but able to render 
them attractive to those who arc little accustomed to think upon 
