Feb. 3, 1 88 1 ] 



NATURE 



2>Z'^ 



White Quibracho. — Notes on the Orchidere formed the subject of 

 an important contribution from Mr. G. Bentham. Orchids early 

 attracted the attention of botanists, though their popularity as 

 objects of cultivation is comparatively a recent phase due in a 

 ijreat measure to Loddige's celebrated collections and to the 

 fashion set up by the Duke of Devonshire in his famous Chats- 

 worth collection, a still further incentive being given liy Chas. 

 Danvin in his studies of their singular modifications of fertilising 

 apparatus and its protecting perianth. In their classification 

 Swartz's labours (1800), thereafter the Richard-.', Dupetit- 

 Thouars, and others, have been superseded by the influx of 

 strange forms then unknown. Rb. Brown first established the 

 principles of their natural arrangement on a solid basis, and 

 Lindley's grouping remains true till the present day. Blume's 

 observations must alwavs take a high rank, and good analytic 

 generic characters and illustrations obtain in the works of Sir 

 W. Hooker, Wight, Griffith, Fitzgerald, and others. The 

 younger Keichenbach has devoted great attention to the group, 

 but we still lack from him a synopsis of c.jntrasted characters 

 adaptive to limitation of tribes and geaera. Dr. Pfester has of 

 late studied their vegetative characters advantageously ; while 

 J. G. Beer proposes divisions founded on mDdifications of the 

 labellum, unfortunately neglecting other structural peculiarities. 

 In reviewing the Lindleyan system Mr. Bentham observes that 

 the primary division based on the consistence of the pollen has 

 not been replaced by any other equally good, althnu^^h it is by 

 no means absolute. He admits that the distinctions dependent 

 upon the so-called caudklcs and gland can scarcely be maintained, 

 independent of the confusion occasioned by the term having been 

 applied to three different parts of the poUinary system. The 

 result of Mr. Bentham's extended examination of all growing and 

 dried specimens procurable, and of the literature extant, is that 

 he divides the order into five tribes and some twenty-seven sub- 

 tribes, as indicated below, and he further gives lengthened ex- 

 planations of these and of the more remarkable genera, &c. : — 

 Orchide.4; : Tril'cl. EpiJciidnv — Subtribes ( i ) Pkurothalleae, (2) 

 Microstylea;, (3) Liparie.-e, (4) Dendrobiea;, (5) Eriese, (6) Bletiese, 

 (7) Coelogynece, (8) Stenoglossie, (9) Loeliea?; Tribe II. Vandei^ — 

 Sub-tribes (i) Eulophiex, (2) Cymbidiens, (3) CyrtopodicEe, (4) 

 .~itanhopiea;, (5) Maxillariere, (6) Oncidieae, (7) Sarcantheie, (8) 

 Notyle^ ; Tribe III. A^eottiea — Sub-tribes (I) \'anilleEe, (2) 

 Corymbieje, (3) Spiranthese, (4) DiurideiE, (5) Aiethuseje, (6) 

 Limodorere ; Tribe IV. Ophrydeie — Sub-tribes (i) Serapiadeje, 

 (2) Habenariea;, (3) Disefe, (4) Coryciese ; Tribe ]'. Cypripedieie. 

 — In a paper by Mr. Edw. J. Lowe on some hybrid British ferns, 

 the author's experiments lead him to believe that Polystic/ium 

 aculeatuir. and P. angulare are forms of one species, and P. 

 lonchitis, Lastrca reciDfa, and L. Alplna are merely mountain 

 forms of P. annulare and L, dilatata respectively. Spores of 

 Athyrium Filix fcemina were mixed, viz., vars. Victoria, with 

 fri%eUi<e and proteum and var. Fieldiie, with PtiUerii and var. 

 Hcrwardiie, with Du BouUt, whence sprang varieties of singular 

 beauty and vigour. — A revision of the genus Vibrissea was a 

 communication by Mr. W. Phillips, which was taken as read. 



Geological Society, Jaiuiary 19. — Robert Etheridge, F.R.S., 

 president, in thi chair. — ^Jabez Church, M.lnst.C.E., George 

 Augustus Fi-eem.an, B.Sc. Loud., Charles Iloryley, C.E., Edwin 

 .Simpson- Baikie, F.L.S., and Charles John Wood, M.lnst.C.E., 

 were elected Fellows of the Society. William Henry Goss was 

 proposed as a Fellow of the Society. — The following communi- 

 cations were read : — Further notes on the family Diastoporidae, 

 Busk, by G. R. Vine, communicated by Prof. P. Martin Duncan, 

 M.B. Lond., F.R.S. In continuing his review of the family of 

 the Diastoporida;, the author stated that upon the question of 

 the classification of the Polyzoa he is inclined to accept the views 

 recently published by the Rev. T. Hincks in preference to the 

 earlier ones enunciated by Prof. Busk. He now described the 

 forms found in the Eias and Oolite, including Pias/opora stroma- 

 toporides. Vine (= liassica, Quenst.), D. ventricosa, Vine, D. 

 oolitica. Vine, D. cricopora. Vine. The author then proceeded 

 to argue against the inclusion of the foliaceous forms in the 

 genus Diastopora, and concluded by giving a definition of the 

 genus, as now limited by himself. — Further notes on the Car- 

 boniferous Fenestellida:, by G. W. Shrubsole, F.G.S. The 

 author pointed out the discrepancies in the descriptions given by 

 Lonsdale, Phillips, McCoy, and King of the genus Fcnestella, as 

 represented in the Silurian, Devonian, Carboniferous, and 

 Permian formations respectively. He then proposed a new 

 definition of his own, and described the following species : — F. 

 tlebeia, McCoy, /". meinbranacea, Phil. F. nodnlos,!, Phil., F. 



polyporala, Phil., F. cj-nssa, McCoy, F. halkinensis, sp. nov. ; 

 and in conclusion he pointed out that the few species to which 

 he has reduced the Carboniferous Fene.^tella; find their repre- 

 sentatives in the North American continent, only one really new 

 form, /'. Norwoodiana, having been described there. 



Physical Society, January 22. — Prof. W. G. Adams in the 

 chair. — New Member, Mr. G. P.ilgrave Simpson, B.Sc. — Notes 

 oir the construction of the photophone, by Prof. Sylvanus 

 Thompson, were read by Prof. Rheinold. Prof. Thompson was 

 led by experiment to question whether Prof. Bell's form of 

 photophone receiver was adapted to give the best results. Theo- 

 retically he finds with a given maximum of incident light dis- 

 tributed unif jrmly over the surface, the change of resistance in 

 a selenium receiver will vary proportionally with its linear dimen- 

 sions, provided its parts be arranged so that on \a hatever scale 

 constructed the normal resistance shall remain the same. A cell 

 « times greater linearly each way will produce n times the varia- 

 tion ia resistance for the same total amount of light. This 

 follows from Prof. W. G. Adams' law that the change in the 

 resistance of selenium is directly as the square root of the illu- 

 minating power. The author also finds that if the thickness of 

 the conducting disks in the enlarged cell be kept the same as 

 before and their number increased ;; times, the change of resist- 

 ance will be ;/■* times as great as before. Selenium cells should 

 therefore be as large as jjossible, and the light should be dis- 

 tributed over them uniformly, not focussed to a point. A conical 

 mirror w ould therefore be better than a parabolic one to receive 

 the beam. Such a reflector would be cheaper to construct, 

 and- there would be a minimum loss by reflection, as the 

 light would fall perpendicularly on a cylindrical cell parallel 

 to its axis. To give the best effect, its angular semi-aperture 

 should be 45", and this will bring the front end of the cell in the 

 same plane as the mouth of the reflector. Prof. Thompson has 

 also construe ed an improved cell by winding parallel %\ires on a 

 cylinder of slate grooved with a double-threaded screw, and 

 filling the interval between them with selenium. This form gives 

 superior eft'ects to Prof. Bell's disk device. Mr. Shelford Bid- 

 well said that long annealing improved the sensitiveness of 

 selenium for photophone purposes. He got the best speech 

 from cells of high total resistance, made with fine wire. The 

 selenium should however have a low specific resistance. With 

 the apparatus he showed at a recent meeting of the Society he 

 could now transmit articles from Nature and the Nimtcinth 

 Century so as to be heard, every word, by the listener. Prof. 

 Guthrie suggested that amorphous phosphorus should be tried in 

 place of selenium as a more permanent substance. — Mr. Glaze- 

 brook, of the Cavendish Laboratoiy, Cambridge, read a paper 

 on the measurement of small resistances and the comparison of 

 the capacities of two condensers. In measuring small resistances 

 by the Wheatstone balance the residts differed on varying the 

 resistance in the battery wires. According to Prof. Chrystal 

 this was due to a thermo-electric effect produced by the hand 

 at the middle point of the divided platinum iridium wire when 

 the contact is made with it. It could be avoided by making 

 this contact first and then making the battery contact. Mr. 

 Glazebrook investigated the effect mathematically and experi- 

 mentally. He suggested that the resistance in the battery wire 

 should be ke]it small in comparison with the other resistances, 

 and then the effect was inappreciable. It could best be elimi- 

 nated by taking two measurements with reversed currents and 

 calculating out. The author next considered the effect of a 

 small leakage in comparing condensers by the Wheatstone 

 balance method. The sensibility of this method is increased 

 by increasing the two resistances and the resistance of the 

 galvanometer. Dr. Hopkinson stated that he had found a 

 modification of this plan to be very promising. For the battery 

 he uses an induction coil, and for the galvanometer a telephone. 

 Thus a high electromotive force and sensibility was obtained. 



Anthropological Institute, January 11. — Edward B. Tylor, 

 F.R.S., president, in the chair. — Mr. G. M. Atkinson exhibited 

 some stone celts from British Guiana.— Mr. John Evans, F.R.S., 

 gave a short account of the proceedings of the International 

 Congress of Prehistoric Archjeology and Anthropology held at 

 Lisbon in September last, at which he had been present in the 

 capacity of delegate from the Institute. One of the excursions 

 vpas to Otta, to inspect the beds in which it was thought that 

 traces of man living in Miocene times had been discovered. 

 This discovery had been accepted by many members of the 

 Congress, but Mr. Evans had not been satisfiei as to the un- 



