Dec. 19, 1878] 



NATURE 



161 



k 



William G auk's detailed " Observations on the Geology of the 

 Black Mountains," a coloured diagram is given. The Appendix 

 contains papers by Mr. Joseph Wright on " Recent Forami- 

 nifera of Down and Antrim," and by Messrs. Swanston and 

 Lapworth on the ".Correlation of the Silurian Rocks of Co. 

 Down." 



The Twentieth Report of the East Kent Natural History 

 Society is, on the whole, satisfactory. It contains abstracts of 

 several good papers read at the meetings. The Society has 

 ninety-three members. 



Excavations in the "Dragon Cave " at Mixniz, St)Tia, have 

 been already noticed (Nature, vol. xviii. p. 618). The diggings 

 made in June, 1878, by the Anthropological Society of Gratz, 

 have brought to light some bones bearing indistinct marks of 

 cutting and percussion. Above the stalagmitic layer over the 

 hearth-stuff some bones were found, in loam, well preserved, 

 but probably derived from an older site. They are greenish, 

 and partly of an intense bluish-green tint ; and Prof. C. Doelter 

 finds that their composition approaches that of turquoise [bone- 

 turquoise ?]. A full account by Prof. R. Hoemes will be found 

 in the Proc. Imp. Geol. Instit, Vienna, August 31, 1878. 



The additions to the Zoological Society's Gardens during the 

 past week include a Yellow Baboon {Cynocephaltts babouin), 

 from W'est Afiica ; two Ring-tailed Lemurs {Lemur cattd), from 

 Madagascar, presented by Mr. G. A. Shaw ; a Green Monkey 

 (Cercopiihecus callitrichus), from ^Yest Africa, presented by Mr. 

 J. W^illiams; a Common Fox {Canis vulpes), British, presented 

 by Mr. Sutton Sharpe ; a Woodcock {Scolopax rusticola), Euro- 

 pean, presented by Messrs. E. and W. H. Davos ; a Conmion 

 Swan {Cygnus olor), European, presented by Capt. Marx ; a 

 Ring-tailed Lemur {Lemur catta), from Madagascar, deposited ; 

 an Ocelot {Felis pardalis), from America ; a Cereopsis Goose 

 (Cereopsis novtz-kollandice), from Australia ; three Yellow-winged 

 Blue Creepers (Ccereba cyanea), from South America, purchased. 



ON HELIOTROPISM IN PLANTS 



•T^HE heliotropic phenomena in plants form the subject of a 

 •*■ monograph by Herr Wiesner, the first part of which has 

 been recently communicated to the Vienna Academy. The 

 following outline from the Anzeiger of the Academy will give 

 an idea of some of the fruits of the author's researches on this 

 important subject. 



The first section treats of the history of the subject. In 

 the second section the author studies the influence of light 

 on heUotropism. The experiments were made in the light of 

 a gas flame which burned under a constant pressure with a 

 uniform intensity (luminous power = 6*5 spermaceti candles). 

 The unit for the measiurement of the light-intensity was the 

 strength of this flame at the distance of one metre. It 

 was found that in heUotropism three cardinal points of light- 

 intensity are to be distinguished ; an upper limit, a lower limit, 

 and between the two an optimum of light intensity. Thus with 

 decreasing intensity of light the strength of the heliotropic effect 

 increases to a certain point, and beyond this point decreases. 

 The lower limit referred to coincides with the lower limit of 

 light-intensity for the stoppage of growth in length, while the 

 upper limit does not coincide, or only occasionally coincides, 

 w-ith the upper limit of light-intensity for growth in length, for 

 in th • case of plants very sensitive heliotropically it lies higher, 

 and in less sensitive plants lower, than the upper limit for growth in 

 length. The mode of arrangement of the experiment in gas-light 

 did not permit of determining in all cases the limiting values of 

 the lijfht-intensities ; tha<, fcr example, the upper limit for the 

 heliotropism of etiolated shoots of Salix alba, and of the hypo- 

 cotj-lous portion of the stem of Viscum albutn, and the lower 

 limit for the heliotropism of the growing stem of vetch could 

 not be ascertained. The former iies above 400, the latter far 

 below o'ooS. The optima were found to lie beUveen o'li (the 

 growing stem of the pea) and 6-25 (etiolated shoots of Salix 

 nlba). Both with gas-light atid with natural Jight it was ascer- 



tained that beyond a certain intensity no 'growth in length 

 occurs. 



The third section treats of the relations between the ref7-angi- 

 bility of the light rays, and the heliotropic effects. The experi- 

 ments were made partly in the objective spectrum, partly in 

 varieties of light, got by sending white light through coloiu-ed 

 solutions. ... It was proved that portions of plants very sensi- 

 tive heliotropically, e.g., growing stems of Vicia sativa, undergo 

 curvatures in all kinds of light, even in ultra -red and ultraviolet, 

 with the exception of yellow. The maximum of the heliotropic 

 force of light lies at the boundary between violet and ultra-violet ; 

 a second (smaller) in the ultra-red. From both maxima the 

 power of the rays to produce heliotropism decreases gradually on 

 to the yellow. Portions of plants little sensitive heliotropically, 

 are no longer influenced by orange, or by red and green, or even 

 (in the case of etiolated shoots of Salix alba) by ultra-red rays. 

 The yellow rays quite stop the heliotropism, for, e.g., in pure 

 red a quicker and stronger heliotropism occurs than in a light 

 which gives yellow besides red. 



In the fourth section experiments are described on the joint 

 action of (positive and negative) heliotropism and (positive and 

 negative) geotropism. It is here shown, inter alia, that, in the 

 case of plants very sensitive heliotropically, the geotropism t, at 

 the optimum of light-intensity, apparently extinguished, even in 

 strongly geotropic organs ; farther, that in many organs (grow- 

 ing stem of the pea), the heliotropic and geotropic powers of 

 curvature disappear simultaneously ; in others, however (stems 

 of cress), the younger portions of the stem are more strongly 

 heliotropic than the older, and the oldest after-growing portions 

 of stem no longer show bendings in the light, but, through 

 drawing action on one side (the heliotropic overhanging point of 

 the stem), show apparently heliotropic curvatures] chiefly due to 

 growth, which are then counteracted by negative geotropism. 



The arguments which go to prove that heliotropism is due to 

 the phenomenon of imequal growth upon unequally-lit sides of 

 an organ are set forth in the next section, and proof is offered 

 that, for heliotropism as well as for growth in length, free oxygen 

 is necessary. 



The last chapter furnishes proof that the conditions for helio- 

 tropism remain constantly the same during its course, and coin- 

 cide with the conditions for growth in length ; fiu-ther, that 

 heliotropism (and the same holds good for geotropism) occurs as 

 a phenomenon of induction. In this chapter it is also shown 

 that when light induces heliotropism in an organ, a fresh 

 heliotropic or geotropic induction meets with resistances, and 

 can only come into action after extinction of action of the first ; 

 and that successive impulses of light and gravity, of which each 

 by itself is capable of producing certain effects, do not have 

 their actions added together when the effects that should be 

 obtained separately are in the same direction, e.g., one and the 

 same side of the organ is helped in its growth in length. 



SOCIETIES AND ACADEMIES 

 London 

 Royal Society, December 5. — " On a Machine for the 

 Solution of Simultaneous Linear Equations," by Sir W^illiam 

 Thomson. Let B^, B^, ... B„ be n bodies each supported on a 

 fixed axis (in practice each is to be supported on knife-edges like 

 the beam of a balance). 



Let /"u, Pax, /31, ... i'w be n pulleys, each pivoted on B^^ ; 



-»12« -'22» ■'35' ' • • • ■* «2 » » » » -^2 > 



I ■'IS' ■'23' ■'33' ••■P'13 ,, ), .O3 ; 



,,, Ci, Cj, iCg .;. C^ be« cords passing over the pulleys ; 

 „ /\, /"u, /"is, P13, ... P^n, El, be the course of Q ; 



>» -Lf^ ■* Sl» ■'22' ^23' ••• *i"> ■^2' »> " ^2 » 



,, .Z>i, E^, Z>2f E^ ... D„, En, be fixed points ; 

 »» A> A h^ -in be the lengths of the cords between D^, E^, 

 and Z?n, Ej, ... and Dn, andE«, along the courses stated above, 

 when B^, B.^, .., B,,, are in particular positions which will be 

 called their zero positions ; 



Let /i + e^, ... 4 -H £j, ... /„ -f <-« be their lengths between the 

 same fixed points, when B^, B.^, ...Bn are turned through angles 

 x^, x^ ... Xn from their zero positions ; 



(II), (12), (13), ...{in), 

 (21), (22), (23), ...(2«), 

 (31)' (32), (33). - (3«), 



