554 



NATURE 



{April lo, 1884 



ties formed during the day. A few of the numbers may 

 be given. In Heliattthus, 964 grms. of starch disap- 

 peared in ten hours from one square metre of leaf- 

 surface. 



In the same plant 9*14 grms. were formed in the same 

 time by the same area of leaf-surface. 



In another case HcUanthits was used, but the leaves 

 were removed from the stem to prevent the passage back 

 of the starch from the mesophyll into the stems. 



A square metre was found to produce starch at the 

 rate of i '648 grms. per hour. 



By combining his experimental results and taking note 

 of all the circumstances, Sachs concludes that twenty to 

 twenty-five grms. of starch per day may be produced by 

 one square metre of leaf-surface as an ordinary occur- 

 rence ; and these numbers are not only not excessive, but 

 experiments show that there are plants which produce 

 much more than those investigated here. 



Some remarkably interesting and important results 

 follow from the consideration of these experimental data. 



They explain why plants are so vigorous during warm 

 nights following upon hot bright days. The more readily 

 the products of assimilation (formed in large quantities 

 during the day) can pass into the growing organs, the 

 better these are nourished, and so forth. 



Leaves used for fodder, &c., must differ in nutritive 

 value to a very great extent if their starchy contents vary 

 so largely during the day and night : it thus becomes of 

 primary importance whether such leaves are gathered in 

 the morning or the evening, in cold or warm weather, &c. 

 The same applies to Tobacco and Tea, &c. It must make 

 a vast difference to the smoker whether his tobacco 

 abounds in carbohydrates or is relatively richer in the 

 alkaloids. It appears that tobacco is habitually cropped 

 in the morning in some countries, a fact which suggests 

 that experience has already shown that a difference in 

 the quality exists ; it will be interesting to incjuire further 

 into these tiiatters. 



Sachs's results will also materially affect the physiologi- 

 cal value of the analyses of leaves. Some of us know 

 how great are the variations met with in analyses of 

 the ash contents of leaves of the same plant. It is clear 

 that, in addition to the age of the leaf, the soil, manure,&c., 

 it is important to know the amount of starch present. It 

 cannot but happen that the mineral matters ebb and flow 

 as well as the starch. The analyses of leaves will also 

 be more valuable for the purposes of physiology if the 

 numbers are stated, not in si)nple percentages, but in 

 terms of one square metre of the leaf-surface. 



The above brief summary of the results obtained by 

 Prof. Sachs by no means does justice to the beauty of 

 his methods, and the masterly way in which they were 

 carried out : it must be admitted by all who understand 

 the value and importance of this work that it is worthy of 

 the great pioneer of vegetable physiology. Moreover, it 

 suggests several matters which require further investiga- 

 tion, and would no doubt yield valuable results to tho^e 

 fortunate enough to have a botanical garden at hand. 

 H. Marshall Ward 



Botanical Laboratory, Owens College 



TELEPHONY AND TELEGRAPHY ON THE 

 SAME WIRES SLMULTANEOUSLY 



FOR the last eighteen months a system has been in 

 active operation in Belgium whereby the ordinary 

 telegraph wires are used to convey telephonic communi- 

 cations at the same time that they are being employed in 

 their ordinary work of transmitting telegraphic messages. 

 This system, the invention of M. Van Rysselberghe, whose 

 previous devices for diminishing the evil effects of induc- 

 tion in the telephone service will be remembered, has 

 lately been described in the Journal Tclegrapltique of 

 Berne by M. J. Banneux of the Belgian Telegraph De- 



partment. Our information is derived from this article 

 and from others by M. Hospitaller. 



The method previously adopted by Van Rysselberghe, 

 to prevent induction from taking place between the tele- 

 graph wires and those running parallel to them used for 

 telephone work, was briefly as follows : — The system of 

 sending the dots and dashes of the code— usually done 

 by depressing and raising a key which suddenly turns on 

 the current and then suddenly turns it off — was modified 

 so that the current should rise gradually and fall gradually 

 in its strength by the introduction of suitable resistances. 

 These were introduced into the circuit at the moment of 



Fig. I 



closing or opening by a simple automatic arrangement 

 worked exactly as before by a key. The result of the 

 gradual opening and gradual closing of the circuit was 

 that the current attained its full strength gradually instead 

 of suddenly, and died away also gradually. And as in- 

 duction from one wire to another depends not on the 

 strength of the current, but on the rate at which the 

 strength changes, this very simple modification had the 

 effect of suppressing induction. Later Van Rysselberghe 

 changed these arrangements for the still simpler device 

 of introducing permanently into the circuit either con- 

 densers or else electromagnets having a high coefficient 



Fig. 2 



of self-induction. These, as is well known to all tele- 

 graphic engineers, retard the rise or fall of an electric 

 current ; they fulfil the conditions required for the working 

 of Van Rysselberghe' s method better than any other 

 device. 



Having got thus far in his devices for destroying induc- 

 tion from one line to another, Van Rysselberghe saw that, 

 as an immediate consequence, it might be concluded that, 

 if the telegraphic currents were thus modified and 

 graduated so that they produced no induction in a neigh- 

 bouring telephone line, they would produce no sound in 

 the telephone if that instrument were itself joined up in 

 the telegraph line. And such was found to be the case 



