November 25, 191 5] 



NATURE 



35» 



\car 1857, when the gold rush to Victoria com- 



nunced. Then a demand sprang up for timber for 



'wellings, culverts, fences, etc., resulting in a deplor- 



iile destruction of valuable trees. The huts built 



re only "wattle and daub" at first, and for these 



If pliable and tough branches of acacia were used. 



rom this use the popular name wattle has been 



i plied to the Australian acacia, and is in common 



-(' to this day. Now, with the establishment in 



107 of a proper State Department of Forests, the 



ire of the timber is assured, and 4,000,000 acres, 



r 7 per cent, of the total area of the State, is a 



served forest area. An account is given of the 



iterent types of Victoria forest, which arc charac- 



I ised chiefly by different species of eucalyptus. Pure 



lests of one species of these trees are not common, 



lough woods may often consist entirely of several 



ilTerent species of eucalyptus. In the highland glens 



Otway and Gippsland groves of the myrtle beech 



\otofagi4s cimniughatiiii) are to be found. 



The journal of the College of Agriculture, Tokyo, 

 or March 20, 1915, contains a short article b)' Dr. S. 

 Honda on the ma.ximal growth of Japanese timber 

 trees. Dr. Honda's article is illustrated by some excel- 

 lent photographs of famous Japanese trees. The sacred 

 uee of Arisan in Formosa {Chamaecyparis jormosen- 

 sis) attains the height of 40 metres, while the seven- 

 forked Cryptomeria of Takaoka reaches 36 metres. 



An extensive paper by Dr. S. Kusano, entitled, 

 " Experimental Studies on the Embryonal Development 

 in an Angiosperm," appears in the Journal of the 

 College of Agriculture, Tokyo, for March 20, 1915. 

 The paper is an elaborate study of the reproductive 

 processes in a saprophytic orchid {Gastrodia data), 

 combining the methods of cytological study and ex- 

 perimental or field work, which, as the author says, 

 "are in most cases not well co-operated." As in some 

 other orchids, the embryo-sac has only four nuclei, 

 instead of the usual eight. Triple fusion takes place, but 

 p.o endosperm is formed. The nuclei in the embryo-sac, 

 which ought to be haploid, are frequently found to 

 ^liow the diploid number of chromosomes (sixteen to 

 ighteen). This points to the possibility of partheno- 

 genesis (apogamy), which, however, could not be in- 

 duced experimentally. The unpoUinated flowers may 

 develop dehiscent capsules and externally normal 

 seeds, but no embryo. Development Is further stimu- 

 lated by certain foreign pollen (especially that of the 

 orchid Blelia), but fertilisation is not effected. The 

 nucleus of an unfertilised egg was sometimes ob- 

 served to divide ; here the nucleus was haploid, so the 

 ase was one of incipient true i)arthenogenesis, as 

 distinguished from apogamy, but it goes no further. 

 Delay in pollination favours poly-embryony, the second 

 embryo being derived from the synergid, which would 

 otherwise provide the " upper polar nucleus." Self- 

 fertilisation, though a chance occurrence in Nature, 

 is quite effective. 



In the Geographical Journal for November (vol. xlvi.. 

 No. 5) Dr. C. Davison gives an account of the earth- 

 quakes in Great Britain from i88c) to 1914. During 

 those twenty-six years the number of earthquakes was 

 no fewer than 357, although not one was accompanied 

 NO. 2404, VOL. 96] 



by crust displacements at the surface. Some year^ 

 were rich in earthquakes, like 191 2 with 74, or 1890 

 with 26, while others, like 1914, 1897, and 1899, had 

 only oi\e. Dr. Davison discusses at length some 

 typical cases, and then the origin of British earth- 

 quakes in general. 



The Sahara in 1915 is the subject of a useful paper 

 by Mr. F. R. Cana in the Geographical Journal for 

 November (vol. xlvi.. No. 5). The summary contains 

 a good deal of information regarding recent French 

 exploration, which is widely scattered and not easy 

 to lay hands on, and it concludes with a discussion 

 of the possibilities of the land. Mr. Cana estimates that 

 over an area of 350,000 square miles, that is, about 

 one-tenth of the Sahara, increased cultivation is pos- 

 sible, and would be profitable. A good deal of well 

 sinking has been done by the French in the Algerian 

 Sahara, with most satisfactory results. Railway ex- 

 tension to some of the larger oases would increase 

 the export of dates. 



The theory that the upper layers of the atmosphere 

 are ionised and therefore conduct electricity, first 

 enunciated by the late Prof. FitzGerald in 1893, has 

 been extensively utilised in recent years to explain the 

 law of decrease of the intensity of radio-telegraphic 

 signals with distance. In an article in the Kcvue 

 ginerale des Sciences for October 30 Prof. H. Nagaoka, 

 of the University of Tokio, attributes this ionisation to 

 two causes. The first is the utra-violet light of the 

 sun, which he believes is capable of ionising the atmo- 

 sphere down to about 40 kilometres from the earth's 

 surface. The second is the stream of electrons emitted 

 by the sun, which, owing to the magnetic fields of 

 the sun and the earth, describe paths far from straight 

 and account for the ionisation of the upper atmosphere 

 at night. The greater height of the reflecting layer 

 at night and the consequent reduction in the number 

 of reflections of the waves at the ionised layer and at 

 the earth's surface account for the better transmission 

 of signals at night. The under concave surface of 

 the ionised layer above a station at which the sun is 

 rising focuses the waves from the west near the sur- 

 face of the earth, and so gives the good signals at 

 dawn. A similar focusing of the waves from the east 

 occurs at sunset. The effect of solar eclipses is ex- 

 plained in the same way, and Prof. Nagaoka points 

 out that as the period of an electrical oscillation on 

 the sun is 65 seconds, there should be a corresponding 

 period in the stray signals at terrestrial stations. He 

 hopes radio-telegraphic observers will succeed in detect- 

 ing this period. 



The October issue of Knowledge contains an article 



on " Eutectics," by J. L. Haughton and D. Hanson. 



In addition to a clear account of the properties and 



structures of these important alloys, the authors give 



a series of eight photographs of typical eutectics. 



These photographs, admirably reproduced on a large 



scale from various originals, are amongst the finest 



illustrations of the kind that have been offered to the 



! general public. The publication of such illustrations 



should go far to convince those who are interested in 



i the industrial employment of alloys that it is worth 



I while to study their structure and to make use of the 



