April 17, 1890] 



NATURE 



573 



and 1888, they would indeed have changed places with no one. 

 After giving further details of the expedition, the lecturer said 

 that on October 30 they sorrowfully bade farewell to Kilima- 

 Njaro, the most beautiful and interesting, as well as the grandest, 

 region in the dark continent. At the conclusion of the paper a 

 series of photographs illustrative of some features of the expedition 

 was exhibited by lime-light, and explained by Mr. Ravenstein. 

 A vote of thanks to Dr. Meyer was proposed by Mr. Joseph 

 Thomson, seconded by Mr. Douglas Freshfield, and heartily 

 accorded. 



A NEW GREEN VEGETABLE COLOURING 

 MA TTER. 1 



'T'HE seeds of the 7 richosanthes palmata are inclosed in a 

 rounded scarlet fruit and embedded in a green bitter pulp. 

 The bitter principle has been shown by Mr. D. Hooper to be a 

 glucoside differing from colocynthin, and he has named it tricho- 

 santhin. The green colouring matter, when freed from the 

 trichosanthin and fatty matter, yields a solution closely resem- 

 bling a solution of cholorophyll. It is green in thin and red in 

 thick layers, and has a red fluorescence. The spectrum, how- 

 ever, is very different. Taking the thickness and strength 

 yielding the most characteristic spectrum, it may be described 

 thus : — The first band begins (penumbra) at W. L. 654 and 

 ends about W. L. 615 ; from this there is a small amount of 

 absorption till the second band begins at W.L. 593'4, and con- 

 tinues to W.L. 566 8, with the maximum absorption near the 

 less refrangible end ; from this there is no perceptible absorption 

 till the third band, which extends from W.L. 548*4 to 534"8 ; 

 there is a fourth band, very faint, with its centre about W.L. 

 5io'6, and a fifth extending from about W.L. 485 to W.L. 

 473 "4. Comparing this with the chlorophyll spectrum, it will be 

 seen that the first band has its centre almost midway between 

 the two chief chlorophyll bands, but that bands IIL, IV., and 

 V. are probably coincident with chlorophyll bands. When the 

 trichosanthes colouring matter is treated with ammonia sulphide 

 the spectrum, is completely changed. The first and most pro- 

 minent band slowly decreases in strength and finally disappears, 

 two new bands appear in the space between bands I. and 11. of 

 the original spectrum ; band II. is apparently displaced towards 

 the violet end and intensified ; and band IV. is greatly widened. 

 Chlorophyll under the same treatment behaves in a totally 

 different manner, and the two spectra become almost comple- 

 mentary. When, however, the trichosanthes colouring matter 

 and chlorophyll are both treated with hydrochloric acid the 

 result is very diff'erent, for the two spectra have now three bands 

 in common. The first band in the trichosanthes spectrum has 

 disappeared, and the spectrum is practically reduced to one 

 of three bands corresponding in position with bands II., III., 

 and IV. of the altered chlorophyll spectrum. Band I. of the 

 chlorophyll spectrum has no representative in the trichosanthes 

 spectrum. The conclusions to be derived from a study of these 

 spectra seem to be that we have in the trichosanthes colouring 

 matter a substance in which the " blue chlorophyll " of Sorby 

 or the " green chlorophyll " of Stokes is replaced by some other 

 substance easily decomposed by reducing agents and acids. 

 Farther, if we assume with Schunck that the product obtained 

 by acting on chlorophyll with hydrochloric acid is the same as 

 Fremy's phyllocyanin, this, too, must be a mixture, one con- 

 stituent of which is obtained by acting on the trichosanthes 

 colouring matter with acid, while the other is, apparently, 

 the unaltered substance yielding band I. in the chlorophyll 

 spectrum. 



SOCIETIES AND ACADEMIES 



London. 



Royal Society, March 13. — "On the Organization of the 



Fossil Plants of the Coal-measures. Part XVII." By William 



Crawford Williamson, LL. D. , F. R. S., Professor of Botany in 



the Owens College, Manchester. 



In 1873 Ifie author described in the Phil. Trans, an inter- 

 esting stem of a plant from the Lower Carboniferous beds of 



' Abstracted ■ from a paper by C. Michie Smith, "On the Absorption 

 Spectra of Certain Vegetable Colouring Matters," read before the Royal 

 Society of Edinburgh, March 17, 1890, and communicated by permission of 

 the Council. 



Lancashire, under the name of Lyginodendron Oldhamium. 

 He also called attention to some petioles of ferns, more fully 

 described in 1874, under the name of Kachiopteris aspera. The 

 former of these plants possessed a highly organized, exogenously 

 developed xylem 2one, whilst the Rachiopteris was only supplied 

 with what looked like closed bundles. Since the dates referred 

 to, a large amount of additional information has been obtained 

 respectii g both these plants. Structures, either not seen, or at 

 least ill- preserved, have now been discovered, throwing fresh 

 light on their affinities ; but most important of all is the proof 

 that the Kachiopteris aspera is now completely identified as the 

 foliar rachis or petiole of the Lyginodendron : hence there is no 

 longer room for doubting that, notwithstanding its indisputable 

 possession of an exogenous vascular zone, the bundles of which 

 exhibit both xylem and phloem elements along with medullary 

 and phloem rays, it has been a true Fern. Though such 

 exogenous developments have now been long known to exist 

 amongst the Calamitean and Lycopodiaceous stems, as well as 

 in other plants of the Carboniferous strata, we have had no 

 evidence until now that the same mode of growth ever occurred 

 amongst the Ferns. Now, however, this Cryptogamic family is 

 shown to be no longer an exceptional one in this respect. All 

 the three great divisions of the Vascular Cryptogams — the 

 Equisetaceae, the Lycopodiacere, and the Homosporous Filices 

 of the primaeval world — exhibited the mode of growth which is 

 confined, at the present day, to the Angiospermous plants. A 

 fui-ther interesting feature of the life of this Lyginodendron is 

 seen in thehistory of the development of its conspicuous medulla. 

 In several of his previous memoirs, notably in his Part IV., the 

 author has demonstrated a peculiarity in the origin of the medulla 

 of the Sigillarian and Lepidodendroid plants. Instead of being 

 a conspicuous structure in the youngest state of the stems and 

 branches of these plants^ as it is in the recent Ferns, and as in 

 most of the living Angiosperms, few or no traces of it are ob- 

 servable in these fossil Lycopodiacere. In them it develops itself 

 in the interior of an apparently solid bundle of tracheae (within 

 which doubtless some obscure cellular germs must be hidden), 

 but ultimately it becomes a large and conspicuous organ. The 

 author has now ascertained that a similar medulla is developed, 

 in precisely the same way, within a large vascular bundle 

 occupying the centre of the very young twigs of the Lyginoden- 

 dron. But in this latter plant other phenomena associated with 

 this development make its history even yet more clear and 

 indisputable than in the case of the Lycopods. The entire 

 history of these anomalous developments adds a new chapter to 

 our records of the physiology of the vegetable kingdom. 



Further light is also thrown upon the structure of the Heter- 

 anglum Grievii, originally described in the author's memoir. 

 Part IV. This plant presents many features in its structure 

 suggesting that it too will ultimately prove to be a Fern. The 

 specimens described in the above memoir, published in 1873, all 

 possessed a more or less developed exogenous xylem zone. But 

 the author has now obtained other, apparently younger examples 

 in which no such zone exists. 



He has discovered the stem of a genus of plants {Bownianites)y 

 hitherto known only by some fruits, the detailed organization of 

 which was originally described by him in the Transactions of 

 the Literary and Philosophical Society of Manchester, in 1 87 1. 

 The structure of this new stem corresponds closely with what is 

 seen in Sphenophyllum and in some forms of Asterophyllites 

 (Memoir v., Phil, Trans., 1874, p. Afl., et seq.). This discovery 

 makes an addition to our knowledge of the great Calamarian 

 family, to which the plant obviously belongs. 



Further demonstrations are also given by the author, illus- 

 trating some features in the history of the true Calamites. 

 Attention is called to the fact that, whilst the large, longitudin- 

 ally-grooved and furrowed inorganic casts of the central medullary 

 cavities of these plants are extremely common, we never find 

 similar casts of the smaller branches. The cause of this is 

 demonstrated in the memoir. In these young twigs the centre 

 of the branch is at first occupied by a parenchymatous medulla. 

 The centre of this medulla becomes absorbed at a very early age, 

 leaving the beginnings of a small fistular cavity in its place ; 

 but, if any plastic mud or sand entered this cavity when the 

 plant was submerged, the surface of such a cast would exhibit 

 no longitudinal groovings, because there would be nothing in 

 the remaining medullary cells surrounding the cast to produce 

 such an effect. It was only when the further growth of the 

 branch was accompanied by a more complete absorption of th«> 

 remaining medullary cells, causing the cavity thus produced tr 



