424 



NA TURE 



[March i, 1894 



MeUorologische Zeitschrifl, December 1893. — Comparison of 

 mercurial barometers with boiling-point thermometers, by 

 Colonel H. Hartl. The author has made several comparisons 

 with the above-mentioned instruments since 1876, and finds 

 that properly constructed and verified thermometers form very 

 good substitutes for barometers, and are capable of giving very 

 accurate determinations of air pressure, especially where it is a 

 question of differences of pressure, rather than of absolute values. 

 They are very useful as a check on the aneroid, and the author 

 considers them indispensable for travellers who wish to deter- 

 mine heights of mountains. — On the determination of differ- 

 ences of temperature and humidity between forest and field, by 

 Dr. J. Schubert. A series of observations was made at Ebers- 

 walde; during 1892 with carefully exposed instruments, the result 

 being that the author considers that much of the difference 

 hitherto found to exist may be due to imperfect exposure of the 

 instruments, and to the times at which the observations were 

 taken. Tie advocates further observations, with the use of the 

 aspiration hygrometer, by which a free circulation of the air 

 about the bulbs is ensured. 



In the number of the Botanical Gazette^ox December 1893, 

 Mr. H. L. Russell completes his interesting account of the 

 bacterial flora of the Atlantic Ocean in the vicinity of Woods 

 Holl, Mass. He finds that bacteria exist in the mud of the 

 ocean-bottom in large numbers, and that they multiply there 

 freely, although they are not so numerous as in fresh water. The 

 geographical distribution of the species is often extensive, and 

 their vertical range exceeds that of the majority of the higher 

 forms of life. The following new species are described : — 

 Bacillus limicola, B. pclagiciis, B. litorostis, and B. iiiaritimiis. 

 Mr. M. A. Carleton describes a series of experiments on the 

 germination of the spores of Uredineae, especially in reference to 

 the efl"ects on the process of different chemicals. In the number 

 for January 1894, Prof Conway Macmillan proposes the terms 

 archenema, protonema, and metanema, for the gametophytic 

 structures below the ferns. Mr. A. Schneider describes the 

 symbiosis of alg£e and bacteria in the tubercles on the roots of 

 Cycas revohita. The bacteria belong to the genus Rhizobizim. 

 Although the roots are abundantly covered with many different 

 kinds of algae, the only species found in the cells of the tubercles 

 was a Nostoc, probably N. commune. This abounds in the 

 palisade-cells, where the iVbi/f^c-colonies appear to take the 

 place, and to serve the function of chloroplastids. 



Ix the yournal of Botany for February, Mr. Jesse Reeves 

 describes the development of the stem and leaves of Physiotium 

 gigantetim, which differ from other acrogenous y ungermannicic 

 in the remarkable peculiarity of having a 2-sided instead of a 

 3-sided apical cell. — The Rev. W. Moyle Rogers adds yet three 

 more new species (?) to the already long list of British Ruhi, 

 viz. R. mollissimus, R. Powellii, R. britannicus. 



With the number for January 1894, the Nuovo Giornale 

 Botanico Italiano commences its new series as the organ of the 

 Italian Botanical Society, under the editorship of Prof. Arcan- 

 geli. The first number consists exclusively of papers on Italian 

 botany. 



SOCIETIES AND ACADEMIES. 



London. 



Royal Society, February i. — "The Action of Heat upon 

 Ethylene." By Vivian B. Lewes. From the work of the 

 earlier observers, the text-books have accepted the equation 



1. C2H,= C.3 + 2H„ 



as representing the decomposition which takes place when 

 ethylene is subjected to a very high temperature, whilst, on the 

 evidence of the work done by Marchand, and Buff and Hoff- 

 man, they represent the change taking place at a lower tempera- 

 ture by the equation 



2. CoH4 = C-l-CH4. 



Berthelot, however, has come to the conclusion that two 

 molecules of ethylene split up at a moderate temperature into 

 acetylene and ethane. 



The author has made an investigation upon the action which 

 takes place at definite temperatures upon the ethylene, the pro- 

 ducts of decomposition being as quickly as possible removed 

 from the heated zone. 



NO. 1270, VOL. 49] 



The gas being passed through 140 mm. of heated tube, no 

 change takes place until a temperature of 800° C. is reached, 

 when traces of acetylene are observed ; between 800° and 900" C. 

 the acetylene increases in quantity, and large quantities of 

 methane are generated, accompanied by liquid products. This 

 action increases until just below 1200° C. when hydrogen begins 

 to appear amongst the products of decomposition, whilst the 

 moment the liberation of hydrogen commences, carbon also is 

 deposited ; and the formation of oil decreases until close upon 

 1500° C. when the decomposition of the ethylene is practically 

 complete, and the products of decomposition are mainly 

 hydrogen with some undecomposed methane, and a copious 

 deposit of carbon. 



When the products of decomposition of the ethylene are 

 heated together for some time, ethane also is produced, but 

 splits up at 900^ C. into ethylene and hydrogen, 



C2H6 = C2H4+H2. 



Analyses of the products of decomposition show that the 

 primary action of heat upon ethylene may be represented by 

 the equation 



3C„Pl4 = 2CoH., + 2CH4; 



whilst tlie final decomposition is as represented by previous 

 observers, 



C.,H4 = C., + 2Ho, 



and that between these two extremes there occur a large number 

 of interactions due to the polymerisation of the acetylene formed 

 from the ethylene, and also at higher temperatures from the 

 methane, according to the equation 



2CH4 = CoH2 + 3Ho. 



February i. — "On Hollow Pyramidal Ice Crystals." By 

 Dr. Karl Grossmann and Joseph Lomas. 



Februarys. — "Researches on the Germination of the Pollen 

 Grain and the Nutrition of the Pollen Tube." By Prof. J. 

 Reynolds Green. 



The whole of the researches described in the paper may be 

 summarised as under : — 



(i) Diastase and ihvertase are both present in pollen grains 

 and can be extracted from them by the same treatment as has 

 been found effectual in the cases of seeds and foliage leaves. 

 The, relative quantities vary a good deal ; while some pollens 

 contain both, others possess only one, which may be either of 

 the two. 



(2) At the onset of germination the amount of both diastase 

 and invertase is usually considerably increased. In one species 

 examined this increase was preceded by a primary diminution. 

 When the pollen grain has lost the power of germinating, the 

 quantity of diastase has considerably decreased. 



(3) The pollen tube is nourished during its growth by plastic 

 reserve material derived from two sources, the store of 

 material in the grain itself, and a further store deposited in the 

 style. 



(4) The reserve store of the pollen grain consists of different 

 materials in different species : starch, dextrin, cane sugar, 

 maltose, and glucose being the forms in which it is found. 



(5) The store in the style consists usually of the same carbo- 

 hydrates, with the exception of dextrin. 



(6) The style itself contains enzymes to assist in preparing the 

 reserve materials for absorption by the pollen tube, while the 

 latter excretes the same ferments during its progress down the 

 conducting tissue. 



(7) The absorption of food material appears to be one cause 

 of the increase of enzyme found to occur during the germina- 

 tion. 



(8) This absorption of food material is usually so active that 

 the reserve store of the pollen grain is often largely increased by 

 a temporary deposition, either in the grain or its tube, of some 

 of the absorbed sugar in the form of starch. 



(9) There is a certain amount of evidence pointing to the 

 existence of zymogens in some pollens, particularly such as 

 germinate in a faintly acid medium. 



February 15. — "On the Straining of the Earth resulting from 

 Secular Cooling." By Charles Davison. 



In this paper the problem as to the total volume of the earth's 

 crust folded and crushed above the surface of zero strain is con- 

 sidered on the supposition that the coefficient of dilatation is not 

 constant, but increases with the temperature. By this means it 



