6i4 



KNOWLEDGE & SCIENTIFIC NEWS. 



[December, 1906. 



which are usuall)' deep-rooted, depend largely on subter- 

 ranean sources for their water supply. Other plants possess 

 two distinct root-systems. One strong- tap-root, which 

 descends, and probably taps a subterranean water supply, 

 while the other system consists of branches given off from 

 the main root, and spread horizontally just under the soil. 

 This last system probably collects water from slight 

 showers, or from the heavy, nightly dews. 



I^ichens are most conspicuous amongst cryptogamic 

 plants. A few ferns, mosses, and even liverworts, occur 

 ill shaded situations. The vegetation of the Karroo is 

 represented by over 1,000 species, included in some eighty- 

 four natural orders. The order Compositce is the most 

 conspicuous family, not only as regards numbers of species 

 and of individuals, but also in the great variety of habit 

 and adaptation to exceptional conditions. 



Coloration of Wood by Fungi. 



Independent of the discoloration of unpainted and sawn 

 wood due to dirt, oxidation, etc., certain other stains of 

 various colours are also often present, more especially on 

 newly-savpn wood. The stains may be blue, brown, blaclc, 

 pink, purple, and yellow. These discolorations have been 

 found to be due to fungi, by Hedgcock, who states that 

 in the United States much injury is done to boards of pine, 

 gum poplar, and other kinds. The blueing of the wood of 

 the western yellow pine is caused by CeratostomcUa pilifera ; 

 this blue stain of pine-wood has long been known in Europe, 

 where it is caused by the same fungus. 



The stain caused by species of Ceratodnmdla, Grapliium, 

 Hormiscium, and Hormoihiidroii, is due to the dark- 

 coloured mycelium permeating the substance of the wood ; 

 no stain exudes from the mycelium. In species of 

 Pemcinium. The discoloration is due to a yellow or red 

 stain from the mycelium, which is taken up by the wood. 

 These stains fade when the wood dries, but reappear when 

 it is moistened. This discoloration caused by Fusai'ium 

 is partly due to the presence of a soluble stain secreted by 

 the fungus, and taken up by the wood, and partly to the 

 presence in the wood of coloured mycelium. 



No mention is made of the brilliant verdegris green 

 colour of wood of ash, oak, etc., caused bv the equally 

 brilliantly coloured cup-shaped fungus, called Pc-iza 

 cerufjinosa, so common in this country, and from which 

 various articles are made, and known as Tunbridge ware. 

 Presumably this fungus is rare or absent from the United 

 States. 



Leaf Variation in Coprosma Baueri. 



Some remarkable changes in form of the leaves of lliis 

 common New Zealand shrub are recorded by Dr. Cockayne. 

 When growing wild on wind-swept cliffs by the sea, where 

 it may receive at times a certain amount of sea-spray, the 

 leaves are fleshy, glossy green on the upper surface, much 

 paler beneath, and the margins recurved. This latter 

 character is sometimes carried to such an extent that each 

 half of the blade is rolled round itself, or the one half m.'iy 

 be rolled round the other, the leaf thus presenting the ap- 

 pearance of a cylinder. The size of such leaves varies to 

 some extent, but an average is 3.2 cm. by 1.9 cm. As 

 Coprosma is amendable to cultivation, it is commonlv used 

 for hedges, and when grown in fairly sheltered situations, 

 away from the influence of the sea, the leaves are much 

 larger, thinner, not quite so glossy as those of wild coastal 

 plants, and quite flat. An average size of such leaves is 

 12.3 cm. by 9.7 cm. If the upper portion of a cultivated 

 hedge happens to be exposed to wind, the leaves show a 

 tendency to curl, the amount of curling being in proportion 

 to the amount of exposure to wind. 



New Ferns from New Zealand. 



Two new ferns are dcscriiu'd by Fi<ld, in Trans. N. Zciil. 

 Inst. One, named Doodia iimlUni<U((i. is allied to I). 

 media, from the same country, differing in having a more 

 compact habit and other important features. The second 

 is named Pteris novce zclaiidia', most nearlv resembling 



P. tremula. The author considers that cresting arises from 

 plants growing under some peculiarly favourable condi- 

 tions, as in several instances specimens become so under 

 cultivation. When a plant breaks into cresting, seedlings 

 from it are apt to exhibit the peculiarity in an exaggerated 

 form. 



CHEMICAL. 



By C. AiNswoRTH Mitchell, B.A. (Oxon.), F.I.C. 



The Bleaching of Flour. 



NuMKROUS methods of bleaching Hour have been devised 

 (see " Knowlelh.k & .Scientihc News," Vol. II., p. 86 ; 

 Vol. III., p. 563), but according to the investigations of M. 

 Fleurent the only processes that have any industrial value are 

 those in which nitrogen peroxide is used as a reagent. Pure 

 oxygen or ozone does not affect the colour, and although 

 ozonised air has a bleaching effect, this is to be attributed 

 solely to the nitrous vapour with which the gas is charged. 

 Moreover, flour treated with ozone acquires a disagreeable 

 odour, which destroys its commercial value. In the bleach- 

 ing with nitrogen peroxide, the oil in the flour combines 

 with the gas, and the weight is increased. This fact affords 

 a means of detecting bleached flour in untreated flour, for 

 on extracting the oil with petroleum spirit,, and converting 

 it into soap, the product has a brownish red colour if nitro- 

 gen peroxide had been used in the bleaching, whereas the 

 Ecap solution from an unbleached flour is rjale yellow. The 

 intensity of the red colour is proportional to the amount of 

 the nitrogen reroxide that has been absorbed by the oil; 

 and jM. Fleurent finds that the test is capable of detecting 

 five per cent, of a bleached product in ordinary flour. The 

 oil in bleached flour becomes acid less readily than in the 

 case of ordinary flour, and it is in this sense only that the 

 bleaching process c-an be said to have any " preservative 

 action." 



An African Arrow^ Poison. 



Dr. Bolton has comniunicaled to the Royal Society the 

 results of his examination of a recently discovered arrow 

 poison, obtained from Ghasi, a town in Northern Nigeria. 

 Dr. Alexander, who forwarded the poison, states that in 

 the fresh condition it is a semi-fluid, black, sticky sub- 

 stance, consisting of or containing the juice of a certain 

 species of fig. It is smeared on sticks, and when required 

 for re-dipping arrows is scraped off and heated. The 

 poison received in London was spread on the ends of two 

 canes, and dusted over with powder from the inside of a 

 gourd. It was a soft, black paste, with a peculiar sweet 

 smell. It dissolved readily in water, with the exception of 

 a small portion consisting chiefly of starch granules. The 

 solution filtered from the insoluble matter was transparent 

 and dark brown, and had a slight acid reaction. The 

 poison was not affected by boiling, and was thus not a true 

 toxine. It acted upon the muscular tissue, and did not 

 appear to have any effect upon the central or peripheral 

 nervous system. Death results through the direct action of 

 the poison upon the muscular system. So potent is the 

 poison that Dr. Alexander reports that a native shot with 

 a poisoned arrow was dead within 25 minutes. The 

 chemical nature of the active principle has not yet been 

 determined. 



Protecting Iron with Paper. 



.\ new and valuable use for paper has been discovered 

 by Mr. L. 11. Barker, in the course of experiments on the 

 methods of protecting iron and steel structures against the 

 action of moisture and atmospheric corrosion. When coats 

 of various kinds of paint were found to be ineffective, trials 

 were made to determine the protective power of paper 

 impregnated with paraflin wax. The iron was first 

 thoroughly cleansed from rust by means of wire brushes 

 and a coating of sticky paint applied. The paper was then 

 piessed tightly on to the surface of the fresh paint, with 

 the edges made to overlap somewhat, and coats of paint at 

 once applied to the surface of the paper. It was found 

 I that iron and steel thus protected remained in the same 



