482 



KNOWLEDGE. 



December, 1910. 



of the animal ? Does it remain unaltered when once formed, 

 or does it become used up and reformed ? 



Stoklasa. Brdlil<. and Ernest iBcr. dcutsch. hot. Gcs., 1909) 

 have carefully re-examined the relationship between chlorophyll 

 and phosphorus in green (chloroplast-containing) leaves. 

 Their analyses, made at intervals from spring to autumn, of 

 Maple leaves, lead them to the conclusion that chlorophyll 

 actually contains phosphorus, contrary to the views of various 

 previous writers. 



ANNU.A.L KINGS IN MONOCOTYLEDONS.— In 

 arboreous (tree-like and shrubby) monocotyledons, there is 

 either no secondary growth in thickness, or a form of 

 secondary growth totally differing from that seen in woody 

 Dicotyledons and Conifers. In various species of Aloe 

 and Yucca, the new tissues formed by the activity of the 

 growing layer show a definite arrangement in zones or " rings." 

 The structure of these zones has recently been investigated by 

 Lindinger iNaturu-. Wochcnschrift. 1909). In Yucca 

 fiJaincntosa and Y. rccurvata each zone has an inner 

 portion poor in vascular bundles, but rich in ground-tissue 

 (corresponding to the "spring wood"), and an outer portion 

 with the reverse characters (corresponding to " autumn 

 wood"). Just as in the wood of Dicotyledons and Conifers, 

 there is a gradual transition from the earlier to the later 

 portion of each year's growth, but a sharp distinction between 

 the last-formed tissue of one year and the first-formed tissue 

 of the following year. In Aloe dichotoina the bundles are 

 evenly scattered, but zoning is produced by the regular 

 alternation of broad layers of soft, large-celled ground-tissue 

 with narrow layers of hard, small-celled tissue. 



CHEMISTRY. 



By C. AiNSWoRTH Mitchell. B.A. (Oxon.), PM.C. 



THE PROPERTIES OF GUARANA.— The natives of 

 Brazil prepare a beverage from the plant known as guarana, 

 the physiological effects of which are very similar to those 

 produced by tea or coffee. An interesting historical outline of 

 the use of the drug is given by Mr. P. H. Marsden in the 

 Annals Trop. Med. and Parasit. (1910. iv, 105). in which 

 are included other particulars of its properties. The plant 

 yielding the commercial product is Panllinia sorbilis. which 

 grows abundantly in certain districts of Brazil, and also in 

 Venezuela and Guiana. 



The seeds of this plant are prepared by being gently heated 

 and pounded in bags to separate the husk from the kernel, 

 and the latter is then crushed to a pulp between stones and 

 mixed with water to form a paste, which is frequently flavoured 

 with cocoa powder, and after being moulded into sticks or 

 cakes is dried in the sun. 



It has hitherto been commonly accepted that the active 

 principle of guarana is the alkaloid caffeine, which is present 

 in tea and coffee, and according to the Spanish Pharmacopoeia 

 guarana must not contain less than three per cent of that 

 alkaloid. 



The general belief as to the presence of caffeine in guarana 

 has been shown to be erroneous by Mr. Nierenstein, who gives 

 a full description of his experiments in the same journal (ibid, 

 p. 115). The alkaloid separated from the drug crystallised in 

 small needles, melting at 217° to 219° C.and after being dried 

 for two hours at 116° C. had a composition corresponding to 

 the formula Cm Hit O21 Nj. The amount of tannin separated 

 from the sample was 4'3 per cent, part of which was in 

 combination with the alkaloid. The exact nature of this 

 alkaloid, provisionally termed guaraniiie, needs further 

 investigation, but the results mentioned above prove that it is 

 certainly not caffeine. 



ACTION OF ULTRA-VIOLET RAYS ON RUBBER. 

 — M. V. Henri, writing in Caoitt. et Gutta-percha (vol. vii. 

 p. 4,371) describes the results of his investigation of 



the effect of ultra-violet rays upon pure and vulcanised 

 indiarubber. Specimens of the pure rubber and samples 

 containing varying proportions of mineral ingredients 

 were exposed, at a distance of about twenty centimetres, 

 to the rays from a mercur\' vapour lamp with quartz 

 tube. In each experiment there was pronounced deterio- 

 ration in the pure material within twenty hours, the rubber 

 becoming darker and more shiny, and showing cracks when 

 stretched. In the case of vulcanised rubber greater resistance 

 was offered to the action of the rays, an exposure of forty- 

 eight to seventy-two hours being required to bring about these 

 changes, while rubber impregnated with mineral matter was 

 affected to a less extent, the deterioration being mainly restricted 

 to the surface. 



The presence of certain substances, such as antimonv 

 sulphide, promoted the decomposition; while other compounds, 

 including litharge, had a retarding influence. Moreover, rubber 

 that had been separated from a solution was attacked more 

 readily than that prepared by evaporation of the latex from 

 the tree. 



Since rubber exposed to the lamp in the absence of oxygen 

 was not affected, the change nnist be attributed to o.xidation 

 promoted by the action of the ultra-violet rays. The rays 

 effecting the deterioration were found to be those of a wave- 

 length of about 3,550, which were absorbed by the rubber. 



From the results of these experiments the practical 

 conclusion is drawn that the envelope of a balloon ought never 

 to be constructed of unvulcanised rubber, and that the cloth 

 used should be coloured with some pigment, such as lead 

 chromate, which would act as a screen in cutting oft" the ultra- 

 violet rays, to which a balloon is the more exposed the greater 

 the height it reaches. 



DIFFUSION OF PETROLEUM.— There are two main 

 theories as to the origin of petroleum; one regarding it as being 

 produced by the direct chemical union of carbon and hydrogen, 

 while the other attributes the production of the deposits to 

 the decomposition of animal or vegetable remains, with the 

 formation of bituminous bodies, lit|uid petroleum oils or gases. 

 This latter \ iew is now the one more generally accepted, and 

 the differences between certain oils, such as those of Pennsyl- 

 vania, which are almost devoid of nitrogenous bodies and 

 sulphur, and those of California, which are rich in those 

 substances, has been explained by the assumption that the 

 former are of vegetable and the latter of animal origin. 



Experiments to obtain evidence on this point have recently 

 been made by Messrs. Gilpin and Bransky (.4;;u';-. Chem. 

 Journ., 1910, xliv, 251), who show that when crude 

 petroleum of the type found in California, Ohio and 

 Texas is made to dift'use upwards through a porous medium, 

 such as fuller's earth, a fractionation takes place, and a 

 product closely resembling Pennsylvanian oil is obtained. On 

 adding water to the fuller's earth the oil that separates from 

 the top of the tube has a lower specific gravity than that 

 separated from the earth in the lower part of the tube, and 

 there is a gradual tendency to the formation of mixtures that 

 will pass unchanged through the earth. There is also a 

 manifest tendency for the unsaturated hydrocarbon and 

 sulphur compounds to be absorbed, the oil at the top containing 

 a much smaller proportion than the heavier fractions at the 

 bottom. In the light of these experiments it is unnecessary 

 to assume a different origin to the two kinds of oil, since 

 diffusion through porous beds in the earth is quite sufficient to 

 account for the difference between them. 



FXONOMIC BIOLOGY. 



By Walter E. Collinge, M.Sc, F.L.S., F.E.S. 



GRAIN WEEVILS. — A correspondent writes to me with 

 reference to my remarks on Calandra granaria last month, 

 and points out how this species, in common with many other 

 weevils, feigns death. Mr. Cole, in his paper, remarks : — " In 

 experimenting with grain weevils, it is important to remember 



