Mar. 30, 1888.] 



SCIENTIFIC NEW^S. 



309 



arrangement of the epidermal cells, as, for instance, in 

 the leaf of the horse chestnut, where the cells are 

 stretched greatly in one direction, the stomates have a 

 longitudinal arrangement along the line of growth, the 

 guard-cells being on each side. They may be distributed 

 singly in the epidermis, or in clusters, and either placed 

 above the surrounding epidermal cells, or below them as 

 is frequently the case in leathery leaves. 



It is by means of a vast number of such little structures 

 that the leaves of land-plants are enabled to evaporate 

 the superfluous water in a plant, and thus to keep it 

 cool, but their most important use is that in evapora- 

 ting moisture from the leaves, they tend to maintain a 

 constant upward flow of sap in the woody fibre of the 

 stems and branches, and by this means to aid to a con- 

 siderable extent in the nutrition of the plant. But prac- 

 tically this evaporation can take place in the presence of 

 sunlight only. When sunlight shines on the sensitive 

 guard-cells before-mentioned it causes them, by absorbing 

 water from the immediate epidermal cells, to swell, and 

 this turgidity produces a tendency to withdraw from each 

 other, and as such withdrawal can take place only in 

 the middle, the ends being fixed, the stomal cavity 

 becomes enlarged. This enlargement is in proportion 

 to the intensity of the sunlight, and on cold dark nights 

 the stomata are closed. The precise manner in which 

 the sunlight acts is not accurately known, but the expla- 

 nation put forward by Professor Sachs, the exceedingly 

 able German botanist, seems to provide a probable solu- 

 tion of the problem, and is as follows : In the guard-cells 

 are found certain starchy substances which are absent 

 from the surrounding cells of the epidermis, and some 

 of these starchy substances being in a state of solution, 

 and one which is thicker than the sap in the immediately 

 adjacent cells, a current of water is set up from the latter 

 through the thin cell wall dividing them from the guard- 

 cells. This takes place in accordance wi:h the physical 

 law of osmosis, by which two liquids of different densi- 

 ties, when separated by a thin membrane, have a 

 tendency to pass into each other through the separating 

 membrane until a balance of density obtains, the thinner 

 liquid generally causing the most rapid current. The 

 increased turgidity thus produced, as has been stated, 

 enlarges the opening of the stoma, but this dilatation 

 though directly due to the increased volume of water in 

 the guard-cells can be traced back to the sunlight which, 

 acting upon tne grains of chlorophyll, formed the starchy 

 substances which in turn set up the current of water from 

 the neighbouring cells, for 'it is only by the combined 

 agency of sunlight and the green matter in plants that 

 starch, an important food-material found largely in their 

 system, can be manufactured out of the carbonic acid 

 gas in the air. Thus — if Sachs be right — the very pro- 

 cess which is engaged in one very important branch of 

 the work of nutrition in plants serves also to set in 

 motion the wonderful apparatus which regulates another 

 branch. It should also be mentioned that the aforesaid 

 authority believes that sunlight also causes the layer of 

 Protoplasm, or living matter which lines the walls of the 

 guard -cells internally, to strongly resist the egress of the 

 water. 



{To be contimud.) 



— ••^;>i>i»^5<f-* — • 



Cider Culture in France. — The number of cider- 

 apple trees in France is about 4,290,000, which would 

 form an avenue extending for more than 1-5,000 miles. 



CORRESPONDENCE. 



The Editor does not hold himself responsible for opinions expressed 

 by his correspondents^ nor can he take notice of a7ionynious com- 

 munications. All letters must be accompanied by the na?ne and 

 address of the writer, not necessarily for publication, but as a 

 guarantee of good faith. 



NAMES OF ANIMALS AND PLANTS. 

 Some of the provincial names of insects and flowers seem to 

 be curious survivals. Thus in the Back Bone of England to 

 the west of Halifax a spider is commonly known as an " arran," 

 and the common heather as "collans." The former name 

 may be either a survival of the Latin " aranea " or a corrup- 

 tion of the French " arraignee," ; but "collans" as a name 

 for heather seems to be the Latin " calluna," now used as the 

 generic name for that plant. Montanus. 



THE INTRODUCTION OF INVENTIONS. 

 Has it ever struck you that the chief difficulty in the way of 

 the inventor comes in after his patent has been secured, and 

 that it cannot be removed by any legislative action ? This 

 difficulty lies in the fact that many of our manufacturers have 

 less enterprise than their Continental and American rivals, 

 and shrink from any novelty. At present the more important 

 an invention the greater is the difficulty in introducing it into 

 practice. S. G. R. 



PSEUDO-ORGANISMS. 

 I have somewhere read an account of experiments per- 

 formed by a M. G. Fournier, in which cells and tubes, apparently 

 organic in their structure, were produced from morganic 

 matter. I should like to know if these experiments have 

 been continued. Is it not possible that such simulacra of 

 living beings may have been produced naturally, and have 

 been mistaken for the fossil-remains of plants? — S. B. 



SPECTROSCOPIC ANALYSIS. 

 I have got a set of absorption-tubes from Browning to illus- 

 trate spectral analysis. Will you or any of your readers 

 kindly explain how to use them ? Spectroscope. 



HIGHER EDUCATION. 

 Whilst our notions of higher education in Britain point 

 chiefly in the direction of more examinations for somebody to 

 pass, the Germans, not yet satisfied with what is being done 

 by their professors, are about founding new institutions for 

 research only. Examinationism can never win against re- 

 search. The man who has learned to make discoveries is a 

 better man than if he had passed examinations by the gross. 



Heliothen. 



HAND-LANTERNS. 



I should like to know if there is such a thing to be had as 

 an electric hand-lantern, giving a fairly powerful light, which 

 could be used in going through woods and game covers at 

 night V The lantern should be very portable, the cost should 

 not be excessive, and the management of the lantern easy. 



If there is no suitable electric lantern at present in the 

 market, what is the best kind of hand-lantern tor the purpose, 

 burning any of the mineral oils, and v/here is it to be pro- 

 cured ? A Subscriber. 



A SINGING HEN CANARY. 

 I have a canary which used to sing (not doing so now), and, 

 of course, it was supposed to be a cock bird. Its song was 

 generally heard before dinner and after tea. But when it 

 discontinued singing it celebrated itself m another way, that 

 of constantly laying eggs, which were found in the morning on 

 the floor of its cage. This bird is still producing eggs, some- 

 times cracked and sometimes with perfect shells, though I do 

 not suppose they would hatch. Have any of your readers 

 known of a similar case? The bird was said by an ex- 

 perienced gentleman to be a "singing hen canary," which 

 explanation appears to be quite correct. F. P. P 



