238 



NA TURE 



[Jiu.v 4, 189 = 



leaves, flowers, and fruit, each taken from the same individual 

 tree, having also been sent to us, we have been enabled to deter- 

 mine that the wood of the s^cXcsAcokanthcraSihimpcri, Benth. 

 and Hook. (Carissa Schimperi, A. DC. ), is used by the Wa 

 Nyika and other tribes inhabiting the coast regions near 

 Momljasa in pre|Mring their arrow-poisons. 



The arrow-poisons of these trilies usually contains a crystalline 

 glucosidal active principle, which, in its chemical properties and 

 Ijharmacological action, is identical with the active principle also 

 separated by us from the wood of Acokaiithcra Sibintpi:ri. 



The complete recognition of the species of Aiokaiithera is of 

 primarj- importance, because several supplies of the wood of 

 unidentified species of Aiokanthera sent to us from East Equa- 

 torial -Africa yielded only a glucosidal active principle which was 

 amorphous. 



The characters of the crystalline active principle w hich we have 

 separated from the wood of the fiilly identified species, Acokan- 

 thera Schimperi, Benth. and Hook., agree with those of the 

 crystalline active principle ouabam, sejiarated by Arnaud from 

 the w ikkI of the unidentified species of Acokanthera, provisionally 

 named Ouabdio^ obtained from North Somaliland, and also from 

 the seeds of an unidentified species of Strophanthus, obtained 

 from West Africa. --Vs, however, the name ouabain is used for 

 three quite different substances, two of w hich are amorphous, we 

 would suggest that, in accordance with a usual custom, the 

 crystalline active principle of Acokanthera Schimperi should tie 

 named acokantherin, and not ouabain. 



The work accomplished by Amott and by Haines in 1853, by 

 Ringer in iSSo, by Kochebraunc and .Arnaud in 1881, by 

 l-iborde in 18S7, by Langlois and \'arigiiy, by dley and 

 Rondeau, and by Gley in 1888, by Sailer in 1891, by I'aschkis 

 in 1892, and by Lewin in 1893, ^^^ been more fully descril)ed in 

 this pajwr than in our preliminary notice of March 23, 1893. 



A detailed examination of the pharmacological action of 

 acokantherin has not led to the discovery of any important 

 qualitative differences between its action and that of Strophanthus 

 hiipiiius and of its active principle slrophanthin, Nshicli was 

 descrilx:d by one of us in 1870, in 1S72, and in 1890. -As, how- 

 ever, a sjiecial interest must be attached to the effects upon the 

 circulation, the experiments upon the heart, blood-vessels, and 

 blood-pressure are described with more detail than those upon 

 other systems. 



The predominant action of acokantherin is that exerted upon 

 striped muscle, and, l>ecause of this action, with |)ossibly an 

 action upon the intrinsic cardio-motor ganglia, the chief effect is 

 produced upon the heart, while the influence exertcil upon the 

 cardio-respiratory centres in the medulla is relatively slight or 

 secondary. 



May 30. — " On the Effect of Pressure of the Surrounding 

 Gas on the Tem|x;rature of the Crater of an Electric Arc Light. 

 Preliminary Notes of Observations made at Daramona, Slreete, 

 Co. Westmeath." By VV. E. Wilson. 



Of late years it has often been assumed that the temperature of 

 the crater forming the [jositive pole of the electric arc is thai of 

 the Ixiiling of carlx)n. The most modern determinations give 

 this [xjint as alxiul 3300'-35C»" C. 



Solar physicists have thought that the photosphere of the sun 

 consists of a layer of clouds formed of jiarticlesof solid carbon. 

 As the temperature of these clouds is certainly not below 

 8000 C, it seems very difficult lo explain how carbon can be 

 iKiiling in the arc at 3500' and yet remain in the solid form in 

 the sun at 8000'. l'res,sure in the solar atmosphere seemed lo 

 tie the most likely cause of this, and yet, from other physical 

 rea-sons, this seemed not probable. 



In order lo investigate whether increased pressure in the gas 

 surrounding an electric arc woulil raise the temperature of 

 the crater, the author used a .strong casl-iron box in the 

 inleri'ir of which an electric arc light could l)e maintained. .At 

 the side of the l)ox was inserted a glass lens, liy which an image 

 <if the crater was formed at a distance <jf 80 cm. When this 

 image was allowed to fall on the a|ierlure of a Boys radio-micro- 

 meter, 'h"- deflections of this instrument showed any variations in 

 " I from the crater. The .-luthor then descrilxis the 



made with this apparatus, an<l shows that by 

 iri> 1..1 nit; liic prosMire of the gas in the box the temperature of 

 the crater is runsider^ibly lowered intead of being raised, and he 

 concludes that ihese experhnents .seem to show that the tem- 

 |ierature of the crater, like that of a filament in an incandescent 

 lamp, depends on how much it is cooled by the surrounding 

 atmosphere, and not on its iK'ing the lcm|ierature at which the 



NO. 1340, VOL. 52] 



vapour of carbon has the same pressure as the surrounding 

 atmosphere. That carbon volatilises in some form at compara- 

 tively low temperatures seems likely, from the way in which the 

 carbon of incandescent lamp filaments is transferred to the gl.iss. 

 The pressure of the vapour of carbon in the arc may consequently 

 be very small, and further it would seem thai the sujiptisilion of 

 high pressures in the solar photosphere, whicli has been referred 

 to in the beginning of this paper, is not borne out by these 

 experiments, and that carbon may exist there in the solid form 

 at very high temperatures although the pressures are compara- 

 tively low. 



June 13. — " Further Observations on the Organisation of 

 the Fossil Plants of the Coal Measures. Part 3. Lyginodcndron 

 and Ileliran^iiiiii.'" By W. C. Williamson, F. R.S., and 

 D. H. Scott,' F.R.S. I 



The authors sum up their conclusions as follows : — 



The vegetative organs of these genera show a remarkable com- 

 bination of fern-like and cycadean characters. The leaves o( 

 Lyginodcndron, which are now well known, are so like fern- 

 leaves, not only in form and venation but in minute structure, 

 that if they stood alone they would, without hesitation, be 

 referred to Filices. -Although many leaves simulate those of 

 ferns in external characters (Stangcria, Thalictrum, &c. ), none 

 are known which at the same time show the characteristic 

 anatomy of fern-leaves. Hence we are led to attach great 

 weight to the characters of the Lyginodcndron foliage. That of 

 Hcterangiuin, though less well preserved, was evidently of the 

 same type. 



In Hcterangium the primary structure of the stem is nuich 

 like that of a monoslelic fern such as Glcichenia, but the leaf- 

 trace bundles closely resemble the foliar bundles of a Cycad. 



In Lyginodcndron the whole structure of the stem suggests a 

 Cycad, but with the remarkable peculiarity thai the bundles 

 here have the structure which in Cycade.e is usually (tiunigh not 

 always) limited to those of the leaf The cycadean characters 

 are loo marked lo be accidental, though the general anatomy of 

 Lyginodcndron is not inconsistent with a close relationship lo 

 ferns, for in OsmiinJa we have a monoslelic fern, with a large 

 ])ilh, collateral bundles in the stem, and concentric ones in the 

 leaf The mere occurrence of secondary growth in a fern-like 

 plant is not surprising, considering that it lakes place in 

 Botrychiiim and Jielminthoslaihys at the present day. 



In various respects Lyginodcndron and Hcterangium have 

 points in common with ("deicheniacex, ( )smundace;v, Marat- 

 tiace^e, Ophioglossex, and Cycadea;. The view of their 

 aftinilies, which we suggesl, is that they are derivatives of an 

 ancient generalised race of ferns, from wliich they have already 

 diverged considerably in the cycadean direction. Of the two 

 genera, Jlctcrangiutn appears to be gei)logicaUy tile more 

 ancient, and certainly stands nearer to the filicinean slock. 

 L^yginodendron , while retaining conspicuous fern-like characters, 

 has advanced much further on cycadean lines. Tliis view by no 

 means involves the improbable assumption that these plants were 

 the .actual ancestors of existing Cycade;e. I low far their 

 <livergence from the fern stock had proceeded cannot be 

 determined until we are acquainted with their organs of re- 

 production. 



The existence of a fossil group on the border land of ferns and 

 Cycads seems now to be well established. Count Solms-Laubach 

 places his Protopilys in this position, which is probal)ly shared 

 tjy Mycloxylon and Poro.xy/on. Messrs. Bertrand aiul ReiiauU 

 h.ave indeed endeavoured to derive the last-named genus from 

 Lycfipodiacca', and have extended tlie same view to Lygino- 

 dcndron and Hctcrangiitvi. In tile latter cases their theory is 

 completely negatived by the organisation of tile leaves, and by 

 many structural details. 



The relation of the genera which we have described to those 

 ancient gymnosperms, the Cordaitctr, will form one of the most 

 interesting palaobolanica! problems of the future. 



The paper is illustr.ated by micro-photographs and liy caniera- 

 lucida drawings. 



Geological Society, June 19. -Dr. Henry Woodwanl, 

 F.R..S., President, in the ch.air. — On the occurrence of radio- 

 laria in chalk, by W. Hill and A. J. Jukes-Browne. The authors 

 noticed the rarity of records of Cretaceous railiolaria, and 

 alluded lo those which have been made, including those by Kilsl 

 and Sollas. They recently discovered spherical liodies resem- 

 bling in form and general appearance certain calcified and par- 

 tially <le.stroyed radiolarian tests from some of the liarl>aclian 



