March l'JOS. 
THE GARDENING WORLD, 
Vll. 
* Gleanings from the World of Science. * 
Linnean Society of London, February I9th. 
Professor S. H. Vines, F.R.S., President, in the Chair. 
The Cowthorpe Oak.— Mr. John Clayton, of Bradford, pre¬ 
sented a set of thirty-two photographs to illustrate the cele- 
brated Cowthorpe Oak, near Wetherby, Yorkshire. From the 
time of John Evelyn this Oak has been described, measured, 
and its age guessed at. Mr. Clayton, in a printed summary of 
twenty-two pages, gives an account of the various observers 
who have mentioned the Oak in question, and many of the 
photographs are designed for comparison with other remark¬ 
able trees, amongst them the Crowhurst Yew in Sussex, the 
great Chestnut at Tortworth, and the Greendale Oak in Wei- 
beck Park. In 1893 careful measurements and photographs 
were made of the tree, on four different visits in January, April, 
June, and October. The author’s deductions from these data 
are, that the' age of the tree has been greatly over-estimated, 
his own belief being that 500 years is the extreme limit of its 
age, from sapling to its present decrepitude and decay. 
Copies of the photographs and text have been limited to 
ten, this copy being presented to the society through Mr. 
William West, F.L.S. The donor was voted the special thanks 
of the society for his gift. 
Essential Oils and Plants.—Dr. George Henderson, F.L.S., 
offered “ Some Remarks on the Possible Uses of Essential Oils 
in the Economy of Plant Life.” Adverting to the well-known 
fact that moisture in the air prevents radiation and consequent 
loss of heat, he suggested that emanations of essential oil from 
plants might possibly prevent damage by night frost during 
the period of flowering, basing his suggestion on Professor 
Tyndall’s researches thirty-two years since, on the presence of 
infinitesimal quantities of essential oil in the air. Tyndall 
found such presence increased the absorptive power of the air 
as regards heat-rays: taking dry air as 1, air saturated with 
moisture as 72, then traces of essential oil rank as follows— 
Rosemary 74, Cassia 109, Spikenard 355, and Aniseed 372. 
Dr. Henderson brought these remarks before the meeting as 
an interesting question for botanic investigation, since essential 
oils are usually regarded as mere waste products. 
A discussion followed, in which Mr. T. Christy, Mr. W. C. 
Worsdell, Mr. G. Massee, Mr. A. P. Young, Professor J. Perci- 
val, and the president took part, and Dr. Henderson replied. 
Electric Pulsation in the Telegraph Plant.—The Rev. T. R. 
R. Stebbing, V.P., having taken the chair, the first paper was 
summarised by the president for the author, “ On the Electric 
Pulsation accompanying Automatic Movements in Desmodium 
gyrans,” by Professor J. C. Bose, C.I.E., M.A., D.Sc. In com¬ 
municating this paper, the president pointed out that it had 
long been known that stimulation of the irritable tissues of 
animals causes a change in their electrical state. When, for 
instance, a nerve is stimulated, an electrical current, known as 
the “ current of action,” is produced, travelling in the tissue from 
the relatively more excited to the relatively less excited portion. 
A good many years ago it was ascertained that a similar 
electrical disturbance is caused by stimulation of parts of plants 
known to be irritable, inasmuch as they respond to a stimulus. 
by a movement. This was demonstrated by Sir John Burdon 
Sanderson in the case of Dionaea, and by Professor Kunkel in 
the case of the Sensitive Plant (Mimosa pudica). It might be 
inferred from this that only those parts of the plant are elec¬ 
trically affected by stimulation which are capable of respond¬ 
ing to a stimulus by a movement. As long ago as 1886 the 
president had pointed out that such an inference was not war¬ 
ranted, a criticism that has been justified by subsequent re¬ 
search. In fact. Professor Bose demonstrated to the society, 
just a year ago, that any living part of a plant, when stimulated 
mechanically, gives an electric response. 
. On the present occasion Professor Bose has broken rew 
ground. In the paper before the society he gives the results 
of his investigation of the question as to whether or not spon¬ 
taneous movements are accompanied by an electric disturb¬ 
ance comparable to that resulting from external stimulation. 
Spontaneous movements are not uncommon in the higher 
plants, but for various reasons there are but few instances 
suitable for an investigation of this kind. The most striking 
case is that of Desmodium gyrans, the Telegraph plant. The 
leaf of this plant is trifoliolate, consisting ox two small lateral 
leaflets and a larger terminal leaflet. The lateral leaflets move 
up and down, like the aims of a semaphore—whence the 
popular name of the plant—the period of" a complete up and 
down movement, in the plants observed, being about three and 
a-half minutes. 
Having placed one electrode on the petiolule of a leaflet, and 
the other on the petiole of the leaf, both in connection with 
a galvanometer, Professor Bose found that the spontaneous 
movement is associated with an electrical disturbance of a 
peculiar kind. There is first a large principal wave of dis¬ 
turbance, followed by a smaller subsidiary wave, the period 
of the former being about one minute, that of the latter about 
two' and a-half minutes. This disturbance is the expression 
of a “ current of action” travelling in the plant from the ex¬ 
citable petiolule to the resting petiole. 
The relation of the double waves of electrical disturbance to 
the movements of the leaflet was found to be this: —The 
principal wave attains its height during the downward move¬ 
ment of the leaflet; the leaflet rests for a brief space at its 
lowest position, during which time electrical recovery takes 
place. The leaflet now moves upwards, and then the second 
or subsidiary wave of electrical disturbance is produced. This 
relation is established by simultaneous records of the move¬ 
ments and of the electrical disturbances, which further show 
that the greater amplitude of the principal wave of electrical 
disturbance is the concomitant of the greater velocity of the 
downward, as compared with the upward, movement of the 
leaflet. 
Some interesting observations are given upon the recurrence 
of periodic fatigue in the leaflets, followed by a restoration of 
activity; as also upon interference effects resulting from plac¬ 
ing the two electrodes upon the petiolules of the two leaflets 
in different phases of movement. 
Discussion followed, Professor II. Marshall Ward, Mr. C. B. 
Clarke, Rev. John Gerard, and the president taking part, 
Ceratanhis Lataniae.—The second paper was by Miss A. L. 
Embleton, B.Sc., communicated by Professor G. B. Howes, 
Sec. L.S., and read by Mr. A. D. Michael for the author, on 
“ Cerataphis Lataniae, a peculiar Aphid.” This insect was 
observed in 1901 on various Orchids in the Cambridge' Univer¬ 
sity Botanic Garden. The first description was by Boisduvql 
in 1867, who considered it a Coccus, and the following year 
Signoret referred it to' a new genus near Aleurodes, styling it 
Boisduvalia Lataniae. In 1879 J. 0. Westwood described a 
similar insect as Asterolecanium orchidearum, “ a new species 
of scale-insect,” occurring o-n Cypripedium, and sparingly on 
Sobralia, Cattleya, and Dendrobium. On comparison this 
proved to be identical with the species under review, which in 
1882 received the name Cerataphis Lataniae from Lichten¬ 
stein. The author gives the detailed synonymy of the creature, 
which is well known to' cultivator’s on the Continent, and’pro¬ 
ceeds to set out its life-history ; in this country it exists in only 
one form, reproduced parthenogenetically, corresponding to an 
aleurodiform stage of a migratory Aphis. The author con¬ 
cludes by suggesting that it is one of the migratory Aphides 
which has been deprived of its usual series of metamorphoses 
owing to an artificial mode of life. 
ilr. G. S. Saunders remarked that many years before he 
had observed the winged female, but. not then being aware of 
its peculiar position, he had not taken special notes of its 
life-history. 
