April, 1915. 



KNOWLEDGE. 



113 



stage than has been supposed ; and, if his observations are 

 correct, they strongly support the theory of the individuality 

 of the chromosome — a point of considerable importance in 

 connection with questions of heredity, since it is generally 

 agreed that hereditary qualities are carried by the chromo- 

 somes, while various questions in inheritance depend upon 

 the question whether the chromosomes do or do not retain 

 their individuality. 



BIOLOGY OF FEGATELLA (CONOCEPHALUM).— 



It has been shown by several writers that Marchantia, 

 Fegatella, and some other members of the Marchantia 

 family of Liverworts are capable of growing in water or in 

 saturated air and in extremely feeble light, and that 

 under these conditions the thallus structure is greatly 

 simplified. The characteristic air-chambers, containing 

 green assimilating filaments, become reduced in extent 

 and simplified in structure in the branches formed in such 

 wet and dark conditions, and the chambers may be absent 

 altogether, the whole thallus also becoming longer and 

 narrower, though chlorophyll is still formed. Miss May- 

 brook (Sew Phytologist, Volume XIII) has studied the 

 modifications in the thallus of plants of Fegatella (Conoce- 

 phalum) conica, a common Liverwort found chiefly beside 

 streams and in other moist places. Her plants were collected 

 from a small cavern in a hedge-bank, and she has worked 

 out, in a very interesting manner, the relation between the 

 structure of plants growing in different light intensities. 

 She concludes from her observations that the absence of 

 air-chambers from the plants found in the wettest and 

 darkest positions is due to the combined effects of darkness 

 and moisture, since in plants growing in decreased intensities 

 of light there is a gradual decrease in the number of chambers 

 per unit of thallus surface and in the size of these chambers. 

 The internal structure of the thallus shows interesting 

 deviations in structure ; for instance, diminished length of 

 the curious beak-like cells which normally terminate the 

 assimilating filaments. The final disappearance of the 

 chambers is apparently dependent upon the moisture 

 factor, for only in those plants showing marked adaptation 

 to a moist habitat were the chambers totally undeveloped, 



CHEMISTRY. 



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



FLUORINE IN MINERAL WATERS.— Recent in- 

 vestigations of MM. Gautier and Clausmann (Bull. Soc. 

 Chini. de France, 1914, No. 15) have shown that all mineral 

 waters contain fluorine, the proportion being greatest in 

 waters of volcanic origin. Thermal alkali bicarbonate 

 waters are particularly rich in the element, although the 

 proportion does not appear to depend upon the temperature. 

 Speaking generally, mineral waters of the same kind show 

 an increase of fluorine accompanying a rise in the total 

 salts. In the case of calcium sulphate waters, whatever 

 their origin, the amount of fluorine is about two milli- 

 grammes, while sea water contains about three milli- 

 grammes per litre, the proportion varying slightly in 

 different places and at different depths. 



THE COLOUR OF METALS.— Various facts in support 

 of the theory that all metals are naturally of the colour ol 

 silver are given by Dr. L. Martiouchck in a Russian chemical 

 journal, and his communication is abstracted in the Bulletin, 

 Sociiti Chimique (1914, Volume XVI, page 751). The yellow 

 tint of certain metals, su< b ai i alcium, has been found to 

 be due to the presence of traces "I impurities, the pure 

 metal being silvery white. Heine has also shown that 

 when copper is spcciallv purified it becomes oi a paler 

 tint, the red colour being apparently the result oi oxidation 

 caused by the presence of lead oxide. Moreover, the metals 

 potassium, sodium, and rubidium are of a yellow colour 

 when obtained by reducing their chlorides with calcium 

 in the presence of air. In this case the yellow tint is due 

 to the nitrogen, and not to the oxygen, in the air. 



POTASH FROM HEDGE CLIPPINGS— Mr. E. J. 

 Russell calls attention in the Journal, Board of Agriculture 

 (1914, Volume XXI, page 694) to the high proportion of 

 potash contained in the ash of bonfires of hedge clippings, 

 weeds, and the like. Samples contained about eleven per 

 cent, of potash (ICO), or nearly as much as kainite. which 

 contains about 12-5 per cent. Hence the ash obtained in 

 normal processes of the form would be worth about forty 

 shillings per ton in normal times, and much more under 

 the present conditions. It is pointed out, however, that 

 precautions must be taken to protect the ash from the rain. 

 since the potassium salts in the ash are readily soluble 

 in water. For example, the potash in a heap of ash was 

 reduced by fifty per cent, after a single night of moderate 

 rain. It is calculated that the hedges from a twenty-acre 

 field would yield an amount of ash equivalent to nearly 

 two hundredweight of kainite, and that the labour of 

 obtaining and burning the clippings would amount to 

 threepence to eightpence per pound of ash. Hence the 

 potash in this form would be expensive if the whole of the 

 operations were specially done for the purpose ; but where 

 the trimming and so on have to be done in any case, the 

 value of the ash would repay the cost of collecting the 

 clippings. 



AN OXIDISABLE VARIETY OF NITROGEN.— It has 

 been found by Mr. T. M. Lowry(PM. Mag., 1914, XXVIII. 

 412) that air that has been subjected first to a silent and 

 then to a sparking electric discharge shows the spectrum 

 of nitrogen peroxide, apparentlv formed by the oxidation 

 of a variety of nitrogen produced under the influence of the 

 discharge. After a few seconds this oxidisable kind of 

 nitrogen reverts to a form which can no longer be oxidised 

 either by oxygen or by ozone, and it is suggested that this 

 momentary production of modified nitrogen may play an 

 important part in the technical processes of fixing atmo- 

 spheric nitrogen. The chemically active form of nitrogen 

 discovered by Mr. Strutt, and described at the time in 

 " Knowledge," cannot be oxidised by ozone under the 

 conditions described. 



GEOGRAPHY. 



By A. Scott, M.A., B.Sc. 



LLASSIFICATION OF SE1 UMENTS.— Although the 

 chief characteristics of the various types of sediments are 

 fairly well known, a paper by A. C. Trowbridge (Jour. 

 Geol., May-June, 1914), in which these characteristics are 

 presented in a tabular form, should prove very useful in 

 the examination of the varii ius dep sits now being laid down 

 on the Earth's surface. Sediments arc divided into aeolian, 

 fluvial, pluvial, talus, glacial (including till and lluvio- 

 glacial), lacustrine, and marine deposits including shallow 

 and deep water). Instead of a division into littoral and non- 

 littoral, lacustrine deposits are divided into those of agitated 

 waters, and those of quiet waters. Similarly, shallow-water 

 marine deposits are classified into those >>t major agitation 

 and those of minor agitation, the former resembling the 

 near-shore lacustrine ami the latter the still-water 

 lacustrine, save in the nature of the tossils Emphasis in- 

 laid on the " lens and pocket structure " of fluvial di 

 and on the intermediate nature of Quvio glacial sediments, 

 which are similar texturally to the fluvial, and lithologically 

 to the glacial. 



STREAM PIRACY -Three interesting case-, showing 

 oi development oi the " int type 



.•I rivei capture, are described in the Publications of the 

 University oi Virginia N i 20, July. 19141 The first case 

 occurs m a rejuvenated river system, where the main stream 

 is entrenching itself, and at the same time approaching, 



by lateral Cutting, a tributary, the junction with which is 



at presenl "in- and .< quartei miles lower down. In the 

 second e.i";e, both the main and tributary streams are 



