April 21, 1870| 
NATURE 
637 
BOTANY 
Variegation of Leaves 
M. EpouarD MorreEN attributes the variegation of leaves to a 
disease which is contagious and which may also be communi- 
cated from one species to another by inoculation, as by the graft- 
ting of a variegated plant on to a healthy stock, or even from the 
stock to a healthy graft. The discoloured or variegated portions 
of a leaf have lost their power of reducing carbonic acid, the 
plants are generally weaker and smaller, their flowers and fruit 
inferior, and they are more liable to be injured by cold. It is 
the sign of an organic disease produced by various causes, as the 
deterioration of the seeds, dampness of the ground, want of light, 
&c. None of the higher classes of plants can exist if entirely de- 
prived of chlorophyll, except such as are parasitic. Some of 
our common variegated cultivated plants, such as Pelargonium 
zonale and Hydrangea, sometimes put out branches which are 
entirely colourless, but these only live a parasitic life on the rest 
of the plant. That the disease is an individual one is shown by 
the fact that it can be propagated by buds, layers, or grafts, even 
by the insertion of the petiole of an infected leaf beneath the 
bark ; while the seeds of variegated individuals will generally 
produce healthy and fully-coloured plants. A.W.B. 
Dimorphic Leaves of Water-plants 
FOLLOWING out his observations on the leaves of Marsilia 
(see NATURE, No. 11 p. 293) Prof. Hildebrand finds that some 
other water plants exhibit a similar peculiarity, as, for instance, 
Polygonum amphibium, and the common arrow-head, Sagittaria 
saggitifolia, frequently producing, when growing in very deep 
water, floating leaves of a different form from the ordinary 
leaves, and exhibiting also differences in structure and in the 
arrangement of the stomata. In the latter species the floating- 
leaves are round and heart-shaped, similar to those of a water- 
lily, instead of arrow-shaped. A.W. B. 
THE MARQUIS DE POMPIGNAN asserts that a remarkably fine 
quality of truffle is cultivated in the vicinity of the Garonne, on a 
district almost solely arenaceous, 
PHYSICS 
Phosphorescence of Gases 
It is a well-known fact, the discovery of which appears due to 
Geissler, of Bonn, that certain highly attenuated gases have the 
power of remaining luminous for a short time after the interrup- 
tion of an electric current by which they have been traversed. 
M. Becquerel attributed this phenomena to the presence of 
oxygen, either free or combined ; M. Morren has since denied that 
pure oxygen itself can exhibit the electric phosphorescence, but that 
it does so when mixed with other gases, more particularly nitrogen. 
Such being the state of the question, M. de la Rive requested 
M. Edouard Sarasin to execute a series of critical experiments, 
an account of which appears in the Archives des Sciences physiques 
et naturelles [135, p- 243] and is summarised in the following 
paragraphs. é , : 
The experiments were made in a large glass jar, 20 centimetres 
in diameter and 30 centimetres high, which was placed on the 
platinum plate of a Babinet’s air-pump, capable of giving a 
yacuum of half a millimetre. The electrodes consisted of two 
‘brass stems, to the extremities of which were screwed two thin 
disks of either brass, platinum, or silver. One of them was 
fixed on the brass screw-plate in the centre of the platinum, the 
other occupied the middle of the flat glass cover of the jar. 
They were also connected with the two poles of a Ruhmkorff’s 
coil of medium size, traversed by the current from four Grove’s 
cells. The interior of the jar communicated with (t) a desiccating 
apparatus, through which the gases were introduced; (2) a 
manometer reading to 0°04 millimetre, and (3) a brass tube in 
which were placed chemically pure gases, contained in bulbs 
which could be broken in a vacuum. 
A number of experiments were made with oxygen, both as 
prepared from potassium chlorate and as yielded by electrolysis. 
Closing his eyes during the intense and blinding glow of the 
continuous discharge, and suddenly opening them on the inter- 
ruption of the current, the observer witnessed, in every case, a 
pale, whitish glimmer, directed, though but momentarily, over the 
path of the preceding display. At and below a pressure of three 
millimetres, but especially at two millimetres, this light fills the 
whole jar. Simultaneously with this occurrence, ozone is pro- 
duced, as proved by testing with finely divided silver; whence, as. 
might be expected, the phosphorescence is considerably diminished 
by employing electrodes of silver. No gas, other than oxygen, 
exhibits this property. Hydrogen, nitrogen, chlorine, iodine- 
vapour, ammonia, coal-gas, hydrogen chloride, and even atmo- 
spheric air, alike failed to produce it. 
When highly concentrated hydrogen sulphate was placed in a 
capsule on the platinum plate, and nitrogen, air, nitrous oxide, 
carbon moxide or dioxide was admitted under the usual condi- 
tions, a phosphorescence was obtained of greater intensity and larger 
duration than in any of the other experiments. Here, also, ozone 
was formed. The presence of silver diminished, the presence of 
hydrogen entirely obliterated the phenomenon. 
Sulphur dioxide gave a feeble but decided phosphorescence. 
Hydrogen nitrateand nitrogen peroxide showed a weak effect. Car- 
bon monoxide and dioxide were very perceptibly phosphorescent, 
and still more on the introduction of hydroge sulphate. It was 
noticed that the addition of this sulphate invariably diminished 
the conductibility of the gas. 
The most curious results were observed with nitrous oxide. 
During the passage of the spark, at ten millimetres (and even 
higher) pressure, a narrow jet appears, of a bright rose colour, 
and exhibiting fine clear striz. Surrounding the jet is a sheath 
of the most brilliant yellow mist of eight to ten millimetres in 
thickness, and perfectly defined. As the jet grows with dimin- 
ishing pressure, this sheath loses its brilliancy, advances farther 
in the jar, and, at two millimetres, fills it entirely. At half a 
millimetre, there is a large rosy jet, with enormous striz extend- 
ing to the walls of the jar, all the interstices being filled with 
yellowish mist. Nitrous oxide shows a phosphorescence at all 
pressures below ten millimetres. At first this is very bright but 
only instantaneous, occupying exactly the place previously assumed 
by the yellow sheath. As the vacuum improves, the phosphor- 
escence becomes more permanent ; and ultimately, at one 
millimetre, and after the interruption of the spark, a yellow mist 
is visible for three seconds, and is bright enough at first to 
illuminate surrounding objects very evidently. 
The preceding experiments lead the author to infer that 
oxygen is the sole cause of the phosphorescence in question, 
which is also and necessarily produced by most oxygenated 
gases. 
SCIENTIFIC SERIALS 
Berg-und huttenmannische Zeitung. The last number of this 
journal contains the following account of a new locality for the 
mineral Knebelite, by L. J. Igelstrém, of Filipstadt. For some 
time Knebelite was only known as occurring at Ilmenau and then 
it was afterwards discovered at Danemora. During a journey in 
the year 1866 he discovered it at the Hillang iron mine in the 
parish of Ludovika, province of Dalarne, Sweden. It is found 
there in great quantities, sometimes in masses twelve feet thick. 
It occurs in the halleflinta, the ore-bearing rock, in connection with 
magnetic iron limestone and traces of magnetic pyrites, with all 
of which it is impregnated. The mineral from Ilmessau and 
Danemora has a pretty constant composition, 'containing 30—32 
silica, 32—34 protoxide of iron, and 34—35 protoxide of man- 
ganese (wide Dana, 1868). The composition of the Knebelite 
from Hillang, which is somewhat different, is as follows :— 
SUC CG oo GO o. BROCE ayaiin 16°74 Oxygen 
Protoxide of iron . 40°96 7 
Protoxide of manganese 19°35 Sp 
Ite 5 5 o 0 oe GARG Dp 
9'09 % 
4°42 (15°38, 
1°87 
” 
10000 
This difference may, perhaps, have been caused by the mineral 
not being entirely free from intermixed magnetic iron. There is, 
nevertheless, no doubt whatever, if one compares the external 
characters, that the Hillangs mineral is the same as that of 
Danemora, and, indeed, it was this identity of external appear- 
ance which occasioned its discovery at Hillangs. Both varieties 
of the mineral have the characteristic of gelatinising with hydro- 
chloric acid. 
In The Journal of the Quekett Microscopical Club for April, is 
the commencement of an article by Mr. M. C. Cooke, on Micro- 
scopic Moulds, restricting the term ‘‘moulds” to the Hypho- 
mycetes, and including all those filamentous fungi which bear 
