No. 107 1, Vol. 42] 



NATURE 



45 



(3) To compare a circular with a rectangular aperture. 



The observations are sufficient to show that the width of the 

 adjustable slit when there is no flow is a perfectly definite mag- 

 nitude, and that a properly constructed apparatus is capable of 

 making measurements of the effective areas of orifices with a 

 very considerable degree of precision. 



"On the Effect of Tension upon Magnetic Changes of 

 Length in Wires of Iron, Nickel, and Cobalt." By Shelford 

 Bidwell, M.A., F.R.S. 



The iron used in these experiments was a piece of soft annealed 

 wire, 07 mm. in diameter and lo cm. in length between the 

 clamps. The weights successively attached to it were equivalent 



I 1950, 1600, 1170, 819, 585, and 351 kilos, per square cm. of 



clion. 



The nickel wire was too mm. long, and 0'65 mm. in diameter. 

 The loads under which it was examined were 2310, 1890, 1400, 

 9S0, 700, and 420 kilos, per sq. cm. 



The cobalt used was a narrow strip measuring icxj mm. by 26 

 mm. by 07 mm., its cross section being, therefore, 1*82 sq. mm. 

 It was not possible to obtain this metal in the form of a wire. 

 [he loads employed for the strip were equivalent to 772, 344, 

 and 75 kilos, per sq. cm. 



In all the experiments the loads were successively applied in 

 tlecreasing order of magnitude, and before every single observa- 

 tion the wire or strip was demagnetized by reversals, without, of 

 course, being removed from the coil. The magnetizing force 

 was carried up to about 375 C.G.S. units for iron and nickel, 

 and 500 units for cobalt. 



The results are given in several tables and curves, and point 

 to the following conclusions : — 



Iron. — Tension diminishes the magnetic elongation of iron, 

 and causes contraction to take place with a smaller magnetizing 

 force. 



Nickel. — In weak fields the magnetic contraction of nickel is 

 diminished by tension. In fields of more than 140 or 150 units, 

 the magnetic contraction is increased by tensional stress up to a 

 certain critical value, depending upon the strength of the field, 

 and diminished by greater tension. 



Cobalt. — The magnetic contraction of cobalt is (for magnetic 

 fields up to 500 G.C.S. units and loads up to 772 kilos, per 

 sq. cm.) practically unaffected by tension. 



Chemical Society, April 3.— Dr. Hugo Miiller, F.R S., 

 \'ice-President, in the chair. — The foUowinaj papers were read : — 

 Note on the hydrosulphides, by Messrs. S. E. Linder and H, 

 I'icton. The authors find that freshly-precipitated metallic 

 sulphides almost always contain hydrogen sulphide, that they 

 are, in fact, hydrosulphides or remnants of hydrosulphides, and 

 that if, instead of adopting the usual plan of passing gas through 

 the solution, the metallic salt be allowed to run slowly into a 

 solution of hydrogen sulphide in water in the absence of too 

 large an excess of acid, a solution of the hydrosulphide is ob- 

 tained which can be freed from dissolved hydrogen sulphide by 

 the current of hydrogen. The copper hvdrosulphide, 7CuS,H2S, 

 and mercury hydrosulphide, 3iHgS, H.,S, are described in the 

 paper. — Researches on the germination of some of the Graminea:, 

 Part I,, by H. T. Brown, F.R.S., and Dr. G. H. Morris. This 

 investigation was undertaken with the view of throwing some 

 light on the complex metabolic processes which takeplac; in the 

 germination of seeds. The authors, during the progress of the 

 inquiry, have examined and experimented with the seeds of a , 

 great number of the grasses, but this, the first part of their paper, ; 

 is confined almost entirely to a consideration of the changes i 

 which take place in barley during the earlier periods of its 

 growth. In recording the visible changes which occur in the 

 seed during germination, it is shown that a disintegration and 

 dissolution of the cell-walls of the endosperm always precede . 

 any attack upon the cell-contents. This breaking down of the 

 cell-wall is shown in a subsequent portion of the paper to depend 

 on the production during germination of a special cellulose- 

 dissolving or "cyto-hydrolytic" enzyme, which, like diastase, is 

 soluble. The action of this enzyme on the cellwa Is of some 

 kinds of vegetable parenchyma is very energetic. The physio- 

 logical importance of this cyto-hydrolyst is very great, for, owing 

 to the non-diffusible nature of the amylo-hydrolytic enzyme — 

 diastase — the previous breaking down of the cell-wall is a neces- 

 sary prelude to the dissolution of the contained starch-granules. 

 The authors show that the appearance of the cyto- and amylo- 

 hydrolysts is due to a specialized secretory function of the layer 

 of columnar epithelium which covers the outer surface of the 



scutellum. It has hitherto been considered that the function of 

 this epithelium was exclusively that of an absorptive tissue : its 

 absorptive as compared with itssecretory functions are, however, 

 of quite secondary importance. The natural food material — 

 starch — does not appear 10 have any special power of stimulating 

 the cells of the epithelium to increased secretion of a diastase, 

 but the flow both of diastase and of the cyto-hydrolytic enzyme 

 from these cells is affected in a very remarkable degree by the 

 presence of certain carbohydrates. Providing the carbohydrate 

 is one which is readily assimilable by the embryo, such as cane- 

 sugar or maltose, secretion of ferment is checked or even entuely 

 inhibited. No such inhibitory action is, however, produced by 

 such substances as mannitol and milk-sugar, which are entirely 

 vvithout nutritive value. The authors' experiments in this direc- 

 tion point to the secretion of the amylo-hydrolytic and cyto- 

 hydrolytic enzymes as being to some extent starvation phenomena. 

 Thepower of secretion possessed by the epithelium is in some way 

 or other so adapted to the requirements of the young plant as to 

 be only exercised when the supply of tissue-forming carbon 

 compounds begins to fail. The histological changes which take 

 place in the cells of the epithelium during secretion are very 

 similar to those which have been observed in certain secretory 

 cells of the alimentary tract of animals, and in the secretory 

 cells of some of the insectivorous plants. The authors confirm 

 the important generalization of Sachs, that the relation of the 

 embryo to the endosperm is that of parasite to host, and they 

 have availed themselves of this relation by cultivating the em- 

 bryo on suitable media after separating it from its endospenn. 

 In this way they have obtained information with regard to the 

 secretory powers of the embryo and the chemical modifications 

 of its absorbed nutriment which it would have been impossible 

 to obtain by any other means. The results of cultivating excised 

 embryos on various nutrient solutions, more especially of the 

 carbohydrates, are recorded, and it is shown that, whilst cane- 

 sugar, invert-sugar, dextrose, lievulose, maltose, raffinose, galac- 

 tose, and glycerol have all more or less nutrient value, milk-sugar 

 and mannitol do not in any way contribute to the growth of 

 tissue in the young plant. Of all the substances tried, cane- 

 sugar has by far the greatest nutritive power. Maltose, although 

 the natural food of the embryo when attached to its endosperm, 

 is decidedly inferior in this respect to cane-sugar. This, at a 

 later point in the paper, is shown to be due to the fact that 

 maltose, directly it is absorbed by the growing embryo, becomes 

 transformed into cane-sugar by the living cells, and in this form 

 is passed from cell to cell. When cane-sugar is supplied ready 

 formed to the young plantlet, there is manifestly a saving of 

 energy to the living cell, which receives its nutriment in a form 

 j in which it is readily available for its requirements. An ex- 

 I amination of the sugars produced during germination, and their 

 I mode of distribution in the grain, have convinced the authors 

 that the transformed starch of the endosperm is absorbed by the 

 embryo in the form of maltose, and that the seat of production 

 of the cane-sugar which all germinated grain contains is the 

 tissues of the embryo itself. The authors are continuing their 

 work upon the germination of the grasses, and are applying the 

 methods described in this first part of their paper to an elucida- 

 tion of the chemical changes which the other reserve materials, 

 especially the proteids, undergo in their passage from the endo- 

 sperm, and of the agencies which are at work in bringing about 

 these transformations. In the discussion which followed the 

 reading of this paper. Prof. Marshall Ward, F.R.S., pointed 

 out that in the seeds of the Graminece, Cyperacea, and other 

 families of plants, there is a peculiar layer of cells, from one to 

 three or more deep, surrounding the starchy endosperm, and 

 distinguished from the latter by containing no starch, but rela- 

 tively large quantities of proteids : this layer belongs to the 

 endosperm, but as the seed ripens, the cells store special pro- 

 teids instead of the starch-grains which predominate in other 

 endosperm cells. In the oat there is such a layer, one cell deep, 

 and it has been shown that, during germination, the dissolution 

 of the starch and the cell-walls of the starch-containing cells 

 begins near the surface of this layer, which itself persists, and the 

 cells of which take up food, and undergo changes so like those of 

 excreting cells that it was concluded that they excrete the 

 diastatic enzyme. Prof. Ward further remarked that the authors' 

 suggestion that more than one enzyme may be excreted accord- 

 ing 10 the nutrition of the cells, and their proof that a cellulose- 

 dissolving enzyme exists in barley, are borne out by various recent 

 researches, and by Wortmann's observations on the behaviour of 

 bacteria in a mixture of starch and proteids. Wortmann proved 



