372 



NA TURE 



{Sept. 3, 1874 



The absolute difference between plants which absorb and 

 nourish themselves by the products of the decomposition of 

 Tilant-structures, and those which make a similar use of animal 

 structures, is not very great. We may imagine that plants acci- 

 dentally permitted the accumulation of insects in some parts of 

 their structure, and the practice became developed because it was 

 found to be useful. It was long ago suggested that the receptacle 

 formed by the connate leaves of Dipsacus might be an incipient 

 ortran of this kind ; and though no insectivorous habit has ever 

 been brought home to that plant, the theory is not improbable. 



Linnanis, and more lately Baillon, have shown how a pitcher 

 of Sarracenia may be regarded as a modification of a leaf of the 

 Nymphxa type. We may imagine such a leaf first becoming 

 hollow, and allowing dchris of different kinds to accumulate ; 

 these would decompose, and a solution would be produced, some 

 of tbe constituents of which would difTuse themselves into the 

 subjacent plant tissues. This is in point of fact absorption, and 

 we may suppose that in the first instance — as perhaps still in 

 Sarracenia fiirpuria—\\\c matter absorbed was merely the 

 saline nutritive products of decomposition, such as ammoniacal 

 salts. The act of digestion — tliat process by which soluble food 

 is reduced without decomposition to a soluble form fitted for 

 absorption — was doubtless subsequently acquired. 



The secretion, however, of fluids by plants is not an unusual 

 phenomenon. In many Aroids a small gland at the apex of the 

 leaves secretes fluid, often in considerable quantities, and the 

 pitcher of Nepenthes is, as I have shown elsewhere, only a gland 

 of this kind, enormously developed. May not, therefore, the 

 wonderful pitchers and carnivorous habit of Nepenthes have 

 both originated by natural selection out of one such honey- 

 secreting gland as we still find developed near that part of the 

 pitcher which represents the tip of the leaf? We may suppose 

 insects to have been entangled in the viscid secretion of such a 

 gland, and to have perished there, being acted upon by those 

 acid secretions that abound in these and most other plants. The 

 subsequent differentiation of the secreting organs of the pitcher 

 into aqueous, saccharine, and acid, would ioWovt pari passu with 

 the evolution of the pitcher itself, according to those mysterious 

 laws which result in the correlation of organs and functions 

 throughout the kingdom of Nature ; and which, in my appre- 

 liension, transcend in wonder and interest those of evolution and 

 the origin of species. 



Delpino has recorded the fact that the spathe of Alocasia 

 secretes an acid fluid which destroys the slugs that visit it, and 

 which he believes subserves its fertilisation. Here any process 

 of nutrition can only be purely secondary. liut the fluids of 

 plants are in the great majority of cases acid, and, when exuded, 

 would be almost certain to bring about some solution in sub- 

 stances with which they came in contact. Thus the acid secre- 

 tions of roots were found by Sachs to corrode polished marble 

 surfaces with which they came in contact, and thus to favour the 

 absorption of mineral matter. 



The solution of albuminoid substances requires, however, 

 besides a suitable acid, the presence of some other albuminoid 

 substance analogous to pepsine. Such substances, however, are 

 frequent in plants. Besides the well-known diastase, which 

 converts the starch of malt into sugar, there are other instances 

 in the synaptase which determines the formation of hydrocyanic 

 acid from emulsine, and the myrosin which similarly induces 

 the formation of oil of mustard. We need not wonder, then, if 

 the fluid secreted by a plant should prove to possess the ingre- 

 dien s necessary for the digestion of insoluble animal matters. 



These remarks will, I hope, lead you to see, that though the 

 processes of plant nutrition are in general extremely different 

 from those of animal nutrition, and involve very simple com- 

 pounds, yet that the protoplasm of plants is not absolutely pro- 

 hibited from availing itself of food, such as that by which the 

 protoplasm of animals is nourished ; under which point of view 

 these phenomena of carnivorous plants will find their place, as 

 one more link in the continuity of nature. 



BRITISH ASSOCIA TION REPORTS 



Report of ilie Committee on Mathematical Tables. 



The objects for which the Committee were appointed at 

 Edinburgh were twofold, viz., the preparation of a list of 

 tables scattered about in books and mathematical journals and 

 transactions, and the calculation of new tables. With regard 

 tj the first object, the tables were roughly divided into three 

 classes, viz. (i) ordinary tallies {such as trigonometrical and 



logarithmic) usually published in books ; (2) tables of con- 

 tinuously varying quantities, generally definite integrals ; and 

 (3) theory of number of tables. On the first class Mr. J. W. 

 L. Glaisher had already written a report, to which it was 

 intended, after the lapse of several years, to add a supplement ; 

 with the second some progress had been made ; while Prof. 

 Cayley proposed to undertake the third. The Committee had 

 to acknowledge the assistance of several foreigners, and chiefly 

 of Prof. Kerens de Haan, who had forwarded to them an account 

 of 128 logarithmic and 105 non-logarithmic tables ; to Dr. Carl 

 Ohrtmann, of Berlin ; and Profs. W. W. Johnson and J. M. 

 Rice, of Annapolis, Maryland. The principal achievement, 

 however, which the Committee had to report related to the 

 second object, and was the completion of the tables of the 

 Elliptic Functions, the commencement of which was noticed in 

 Nature nearly two years ago, and on which six or seven com- 

 puters, under the superintendence of Mr. J. Glaisher, F. R.S., 

 and Mr. J. W. L. Glaisher, have since been constantly engaged. 

 These tables (which are of double entry) give the four theta 

 functions, which form the numerators and denominators of the 

 three elliptic functions, and their logarithms for 8, 100 argu- 

 ments ; so that they contain nearly 65,000 tabular results. The 

 calculation has been carried to ten figures, but only eight will be 

 printed, the tabular portion of the work occupying 360 pages. 

 Parts of the introduction will be written by Prof. Cayley, Sir 

 William Thomson, and Prof. 11. J. .S. Smith, and it is hoped 

 that before the next meeting of the Association the whole work, 

 which will form one of the largest tables that have appeared as the 

 result of an original calculation, will be in print. It is perhaps 

 desirable to state that the elliptic functions which have thus been 

 tabulated are, as it were, generalised sines and cosines. Sines and 

 cosines may be combined so as to represent any singly periodic func- 

 tion, as is well known ; and in the same way elliptic functions repre- 

 sent every possible doubly periodic function ; and no quantities can 

 be of a higher degree of periodicity. The elliptic functions (which 

 are in a sense inverse to Legendre's Elliptic Integrals) are thus 

 quantities of the highest importance and generality in mathe- 

 matics, and they are daily becoming of more importance in 

 physics. They appear conspicuously in the investigation of the 

 motion of a rigid body and in electrostatics, and have also 

 numerous applications in the theory of numbers. The calcula- 

 tions were just completed before the meeting, and the printing 

 will commence immediately : it is intended that the tables shall 

 be stereotyped to ensure freedom from typographical errors. 



Report of the Committee on the Nomenclature of Dynamical and 

 Elcitrical L ^nits. 



They have circulated numerous copies of their last year's 

 report among scientific men both at home and abroad. They 

 believe, however, that in order to render their recommendations 

 fiUly available for science teaching and scientific work, a full and 

 popular exposition of the whole subject of physical units is neces- 

 sary, together with a collection of examples (tabular and other- 

 wise) illustrating the application of systematic units to a variety 

 of physical measurements. Students usually find peculiar diffi- 

 culty in questions relating to units ; and even the experienced 

 scientific calculator is glad to have before him concrete exam- 

 ples with which to compare his own results as a security against 

 misapprehension or mistake. 



Some members of the Committee have been preparing a small 

 volume of Illustrations of the C. G. S. System (centimetre- 

 gramme-second system) intended to meet this want. The Com- 

 mittee do not desire to be re-appointed ; at all events at present. 



On Siemens' Pyrometer, by Prof. G. C. Foster. 



The committee appointed to report upon Siemens' pyrometer 

 has sought to determine whether or no the resistance is altered 

 after exposure to high temperatures. The resistance was 

 measured by means of Wheatstone's Bridge. An arrangement 

 was adojited whereby the heat of the connecting wires was pre- 

 vented from affecting the measurements. As a long thick iron 

 tube surrounded the platinum coil of the pyrometer, it was impos- 

 sible, in order to secure a standard temperature, to plunge the 

 instrument into ice-cold water, because, owing to the conductivity 

 of the iron, there was no certainty that the pyrom.eter wire was 

 actually at the same temperature as the water. The temperature 

 of io°, which was near the usual atmospheric temperature, was 

 adopted as the standard. 



Four instruments were examined : in one of them (i) the coil 

 was surrounded by an iron sheath, in (2) and (3) a piece of stout 

 platinum foil surrounded the cylinder between the iron sheath 

 and the coil. In (4) there was no iron sheatli, but a platinum 



