Feb. 26, 1685] 



NA TURE 



399 



comparatively exposed situations more compact leaves may be 

 more suitable. It was pointed out that finely cut leaves are 

 common among low herbs, and that some families which among 

 the low and herbaceous species have such leaves, in shrubby or 

 ligneous ones have leaves more or less like those of the laurel or 

 beech. 



Much light is thrown on the subject by a study of the 

 leaves of seedlings. Thus the furze has at first trifoliate 

 leaves, which gradually pass into spines. This shows that 

 the furze is descended from ancestors which had trifoliate 

 leaves, as so many of its congeners have now. Similarly, in 

 some species which when mature have palmate leaves, those of 

 the seedling are heart-shaped. He thought that perhaps in 

 all cases the palmate form was derived from the heart-shaped. 

 He then pointed out that if there were some definite form told 

 off for each species then a similar rule ought to hold good for 

 each genus. The species of a genus might well differ more 

 from one another than the varieties of any particular spe- 

 cies ; the generic type might be, so to say, less closely 

 limited ; but Mill there ought to be some type characteristic of 

 the genus. 



He took, then, one genus, that of Senecio (the groundsel). 

 Now in addition to Senecios more or less re : embling the common 

 groundsel, there were species with leaves like the daisy, bushy 

 species with leaves like rosemary and the box, small trees with 

 leaves like the laurel and the poplar, climbing species like the 

 convolvulus and bryony. In fact the list is a very long one, and 

 shows that there is no definite type of leaf in the genus, but that 

 the form in the various species depends on the condition of the 

 species. From these and other considerations he concluded that 

 of leaves did not depend on any inherent tendency, 

 but i" the structure and organisation, the habits and require- 

 ments of the plant. Of course it might be that the present form 

 had reference to former and not to present conditions. Nor 

 did it follow that the adaptation need be perfect. The tend- 

 ency existed, just as water tends to find its level. This rendered 

 the problem all the more complex and difficult. 



The lecture was illustrated by numerous diagnms and speci- 



Sirjohn concluded by saying the subject presented 



a wide and interesting field of study, for if he were correct in his 



contention every one of the almost infinite forms of leaves must 



have some cause and explanation. 



SCIENTIFIC SERIALS 



Journal of the Russian Chemical and Physical Society, vol. 



xvi. fa=c. 8. — On the oxidation of acetones, by E. Wagner (first 

 paper dealing with their behaviour towards chromic acid). — On 

 the specific volumes of chlorine, iodine, and bro rine in organic 



Is, by M. Schalfejeff (second paper). For chlorine they 

 gradually rise with the increase of the number of equivalents en- 

 tering into combination, gradually reaching 21, 24, and 27 ; for 

 bromine they are 24, 27, and 30 ; and for iodine, 26 to 27. — Addi- 

 tion of methylamine to methylglycidic acid, by M. Zelinsky. — 

 ( Mi Astrakhanite, by W.. Markovnikoff. — On the influence of the 

 lineary compression of iron, steel, and nickel rods on their 

 I . Bakmetieff. From a varied series of experi- 

 ments the author arrives at a series of conclusions, showing that 

 compression of iron rods exercises a very notable influent 

 magnetisation, and that the phenomena depend upon the rods 

 having been, or not, formerly submitted to repeated compres- 

 sion ; all kinds of iron and steel display the influence of com- 

 pression — soft iron and steel at a higher degree than hard iron 



/ of rotating molecular magi: 

 explain all observed phenomena. — On an amperomeire based on 

 the electrothermic phenomenon of Pelletier, by N. Hesehus. — 

 < )n the regular forms taken by powders, by Th. Petrushevsky 

 (second paper dealing with the shapes taken by heaps of 



in surfaces limited by curves, or polygones with enter- 

 ing angles). — Al-o on the dilatation of liquids ; an answer to 

 I irius, by D. Mendeleeff. — An answer to M. I ky, 



l.ewitsch. — An answer to M. Sokoloflf, \. B 

 being a further mathematical inquiry into the forces of molecular 

 attraction. — An answer to M. Petroff, by M. Kraevitsch. — We 

 notice an innovation in this fasciculum of the Journal. It con- 



liled minutes of the proceedings of the Mr. 

 Chemical Section of the Moscow Society of Lovers of Natural 

 Science. 



Sitzungsberichte der Physicalisch-medicinishen Societat zu 

 No. 16, October, 1883, to October, 1SS4.— Remarks 

 on the phenomenon of phosphorescence in connection with the 

 description of an instrument designed for studying the effect of 

 the various spectral rays, and especially the ultra-red on phos- 

 phorising substances, by E. Lommel. — On the fluorescence 

 of calcspar, by E. Lommel. — On the reduction of algebraic 

 differential expressions to normal forms, by M. Noether. — Con- 

 tributions to the knowledge of the Chytridiacece and other fung- 

 oid organisms, with thirty-seven illustrations, by D. C. Fisch. 

 — On the malaria and intermittent fevers of the Erlangen district, 

 by Prof. F. Penzoldt. — On the presence of microscopic organisms 

 in the tissues of animals in the normal state, by Dr. Hanser. — 

 Test of the sensitiveness of the visual organ to direct and oblique 

 luminous rays, by Dr. Louis Weinberg. — On algebraic differ- 

 ential expressions, and on Jacobi's reverse problem, by M. 

 Noether. — On the systematic position of the yeast fungus, by M. 

 Reess. — On two new species of Chytridiacea?, by C. Fisch. — On 

 the nerves of temperature and touch in the animal system, by J. 

 Rosenthal. — On a means of determining the quantity of carbonic 

 acid present in the atmosphere of rooms, by J. Rosenthal. — On 

 the phenomenon of Uraemia, by Dr. R. Fleischer. — Toxicologic 

 researches from the physiological standpoint, by J. Rosenthal. — 

 On vertigo caused by intestinal affections, by W. Lenbe. — Ex- 

 periments on the hatching of bird's eggs whose shells had suffered 

 lesion, by Prof. L. Gerlach. — On Oidema, by Dr. R. Fleischer. 

 — On the surgical operation of opening the mastoid process, by 

 Dr. W. Kiesselbach. — On the life-history and pathological proper- 

 ties of a species of bacteria causing putrefaction, by Dr. G. 

 Hauser. — On the histiology of primary carcinom in the osseous 

 system, by Dr. von During. — On a case of lingual tuberculosis, 

 by Dr. Ernst Graser. — On the after-treatment of external 

 urethrotomy, by H. Knoch. 



Rivista Scien'.ifica-Indnslriale, December 31, 1884. — On the 

 electric conductivity of the alcoholic solutions of some chlorides, 

 by Dr. Joseph Vicentini. — Memoir on the variations in the elec- 

 tric resistance of solid and pure metal wires according to the 

 temperature (continued), by Prof. Angelo Euro. 



SOCIETIES AND ACADEMIES 



London 



Royal Society, February 12. — " On Underground Tem- 

 peratures, with Observations on the Conductivity of Rocks, on 

 the Thermal Effects of Saturation and Imbibition, and on a 

 Special Source of Heat in Mountain Ranges." By Joseph 

 Prestwich, M.A., F.R.S., Professor of Geology in the Uni- 

 versity of Oxford. 



The author remarks on the difference of opinion between 

 physicists and geologists respecting the probable thickness of the 

 outer crust of the earth — the former on the strength of its great 

 rigidity and the absence of tides, contending for a maximum 

 thickness and comparative solidity of the whole mass ; while 

 the latter, in general, on the evidence of volcanic action, the 

 crumpling and folding of the strata in mountain ranges, its 

 general flexibility down to the most recent geological times, and 

 the rate of increase of temperature in descending beneath the 

 surface, contend for a crust of minimum thickness as alone com - 

 patible with these phenomena. 



The question of underground temperature, which is a subject 

 equally affecting the argument on both sides, had engaged the 

 author's attention in connection with an inquiry respecting vol- 

 canic action, and he was induced to tabulate the results to see how 

 far the usually received rates of increase were affected by various 

 interfering causes — not that most of them had not received due 

 attention, but it was a question whether sufficient allowance had 

 been made for them. 



Although Gensanne's first experiments were made in 1740, 

 and others were subsequently made by Daubuisson, Saussure, 

 and Cordier, in coal and other mines, it was not until the con- 

 struction of deep artesian wells commenced in the second quarter 

 of this century, and Walferdin introduced his overflow thermo- 

 meter, and precautions were taken against pressure, that the 

 more reliable observations were made and admirably discussed 

 ago. The Coal Commission of 1S66 collected a mass of 

 important evidence bearing on the question, and in 1S67 a Com- 

 mittee of the British Association was appointed to collect further 

 information. Under the able superintendence of Prof. Everett, 

 a series of valuable experiment-, with improved instruments has 



