428 



NA TURE 



[March 2, 1893 



plant to another, through the intercellular spaces, is governed I 

 by other laws. It was at first thought that the rate of move- 

 ment would correspond to that in capillary tubes, according to 

 the well-known law of Poisenille, that it is proportional to the 

 fourth power of the diameter, divided by the length of the 

 tube. But upon testing the matter two years ago, Wiesner 

 found that owing to the extreme minuteness of the mtercellular 

 spaces, and their zigzagged and branched condition, this 

 law does not hold, neither does the movement prove to be 

 proportional to the density of the gases. The discovery of the 

 law of the rate of movement of gases in intercellular spaces, 

 that is, the transpiration of gases, is, therefore, yet to be dis- 

 covered, together with other interesting facts pertaining to the 

 subject. Poisenille's law does, however, hold good for the 

 movement of gases in the woody ducts, but here it is of limited 

 application, for these do not connect with one another, with 

 the intercellular spaces, or with the exterior of the plant. 



The walls of most cells, ducts, and surface covering of plants, 

 except as already mentioned, are imperforate, that is without 

 any openings that can be demonstrated by the microscope. If 

 gases pass through them, it must be in accordance with some 

 law of diffusion, or osmosis. Many experiments in this line 

 have been tried, and the results have been of the most diverse 

 character. It is impossible to give a fair idea of the subject in 

 the time at my disposal, and it must suffice to mention a few 

 bare facts. 



The most astonishing and important results were obtained 

 by Wiesner, in experiments conducted at Vienna, two years 

 since. It would be a most natural interpretation, it seems to 

 me, to think that the gases are forced from one cell to another, 

 through the cell walls by differences in pressure. Wiesner 

 found, however, that it is impossible to force gases through 

 cell walls of any kind whatever, by any pressure they will 

 stand, acting for any length of time. For instance, a bit of 

 grape skin held up a column of mercury, 70 centimetres high, 

 for seventy-five days, and a piece of cherry skin withstood a 

 pressure of 3 atmospheres for twenty-four hours. Similar ex- 

 periments were tried with cuticularised, suberised, liquefied and 

 simple cellulose tissues from many sources, and with uniformly 

 the same results, whether the tissues were moist or dry, alive or 

 dead. 



But in the same set of experiments it was found that if gases 

 cannot be forced through cell walls, they will readily pass 

 through by simple osmotic diffusion. All cells permit the pas- 

 sage of gases by diffusion when moist, dependent upon the 

 coefficient of absorption and the density of the gas. Cuticular 

 and corky formations also permit the passage of gases when 

 dry. Thus we see that gases may be forced through the 

 stomata, or breathing pores, by varying pressure, but can only 

 pass through the epidermis and bark of plants by diffusion. 

 We therefore arrive at the conclusion that the gases inside and 

 outside of the plant are brought to an equilibrium by direct 

 interchange through the stomata and intercellular spaces, 

 aided by the comparatively slow process of diffusion through 

 the whole surface of the plant, bQth above and below ground. 



J. C. Arthur. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 



Oxford.— The Curators of the Hope Collections will pro- 

 ceed to the election of a Hope Profe>sor in Trinity Term 1893. 

 Candidates for the Professorship, of which the emoluments are 

 ;i^48o per annum, are required to send in their applications, 

 together with such evidence of their qualifications as they may 

 wish to submit to the Curators, on or before May i, 189^, to 

 the Registrar of the University, Clarendon Buildings, Oxford. 

 The duties of the Hope Professor are, to give public lectures 

 and private instruction on zoology with special reference to the 

 Aniculata, to arrange and superintend the Hope collection of 

 annulose animals, and to reside in the University for the term of 

 eight months in every academical year between October i and 

 July 15- 



Physiological Departtnent. — It is satisfactory to note that the 

 number of students in this department is greater than in any 

 previous corresponding term. The increase is due not only to 

 the larger number of candidates for the M.B. degree, but also 

 to a larger number of candidates for honours in Physiology in 

 the Honour School of Natural Science. The course of study 



NO. 12 18, VOL. 47] 



during the term has comprised lectures on the general subjects 

 of the Honour School by the Waynflete Professor on the 

 physiology of nutrition, by Dr. J. S. Haldane ; and on the nervous 

 System, by Dr. E. Starling. Mr. Leonard Hill has undertaken 

 the course of lectures on elementary physiology. Practical 

 instruction has been carried on under the superintendence of 

 Dr. Haldane and Mr. M. S. Pembrey. 



SCIENTIFIC SERIALS. 



Bulletin 0/ the New York Mat he in at ic a I Society, Vol. ii. No. 

 4 (New York, 1893). — The contents of this number are an 

 abstract of a paper (read before the Society, June 4, 1892) by 

 Prof. W. Woolsey Johnson, entitled "On Peters's Formula for 

 Probable Error" (pp. 57-61). A clear abstract of Engel and 

 Sophus Lie's Theorie der Transformationsgruppen, by C. H. 

 Chapman (pp. 61-71), and a similar account of U. Dini's work 

 on the theory of functions of a real variable, by J. Harkness (pp. 

 71-76). Notes and new publications complete the number. 



Bulletin de V Academie Roy ale de Belgique, No. 12. — An un- 

 published corollary of Kepler's laws, by F. Folic. A deduction 

 of Dewar's empirical formula for the ratios of the mean velocities 

 of the planets from Kepler's third law. — On the common cause 

 of surface tension and evaporation of liquids (preliminary note) 

 by G. Van der Mensbrugghe. The author endeavoured to show 

 in 1886 that the particles of a liquid are at distances apart which 

 increase as we approach the surface, and that therefore the 

 tension is greatest at the surface. Following up this view, he 

 regards surface tension as the elastic force due to tangential dis- 

 placement of surface particles, and evaporation as produced by 

 molecular displacement beyond a certain limit in a direction 

 normal to the surface. He predicts that a liquid of high surface 

 tension will be able to evaporate across another liquid which has 

 a lower density and surface tension, and does not mix with the 

 former. — On a new optical illusion, by M. J. Delboeuf — On the 

 reduction of invariant functions in the system of geometric 

 variables, by Jacques Deruyts. — Construction of a complex 

 system of straight lines of the second order and the second class, 

 by Fran9ois Deruyts. — Contribution to the study of diastase, by 

 Jules Vuylsteke. — Pupine, a new animal substance, by A. B. 

 Griffiths. — Two experimental verifications relative to refraction 

 in crystals, by J. Verschaffelt. Billet has calculated that if 

 refraction takes place on a cleavage face of a crystal of Iceland 

 spar, the angle of refraction for the extraordinary ray corres- 

 ponding to normal incidence is 6°12', and that the ray is normal 

 with an incidence of 9° 49'. M. Verschaffelt has determined 

 these angles experimentally, and found them to be 6° 9' and 

 9° 45' respectively, thus showing a close agreement with the 

 theoretical values. — On the bacterian fermentation of sardines, 

 by M. A. B. Griffiths. — On prejudices in astronomy, by M. F. 

 Folic. — On the constitution of matter and modern physics, by 

 P. de Heen. 



Ann. deir Ufficio Cent. Meteor e Geodinamico, ser. secund., 

 part iii. vol. xi. 1889. Roma, 1892. — Fumo di Vulcano veduto 

 dair Osservatorio di Palermo durante I'eruzione del 1889, by A. 

 Ricco. — From the obervatory terrace (72m. above sea level) the 

 summits of some of the Lipari islands are visible, but that of 

 Vulcano (140km. distant) is not so. Any smoke or vapour that 

 exceeds 300m. in height can, however, be seen. The author was 

 not successful in either photographing or measuring the dimen- 

 sions of the smoke cloud, which were, however, estimated by 

 comparison with the size of Alicuri, which had been carefully 

 determined. At the commencement of the observations 

 (January 6, 1889) the smoke column reached a height lo^km. 

 and had the form of the pine tree. Several drawings are given, 

 and the form assumed in some cases is very curious. The paper 

 terminates with some thermodynamical calculations, which are 

 very interesting, but unfortunately based on false premises. The 

 author supposes that the eruption was caused,by the access of the 

 sea-water. He supposes this to be at sea level, and calculating 

 the pressure at this point, concludes the vapour was produced 

 from water heated to 196° C. only. He seems to be unacquainted 

 with the solution of HjO in the fluid volcanic glass, the vesiculation 

 and escape of vapour from it, involving so many data with which 

 the physicist has not yet supplied us, as to make any calcula- 

 tions of such a nature of a highly romantic rather than of practical 

 use. 



