146 



THE AGRICULTURAL NEWS. 



May 



1915. 



The point broughl out in those remarks is a sug- 

 gestive one and indicates the immense field which lies 

 before the planl physiologist. It is especially interest- 

 ing in regard to the West [ndi - ind 

 starches cons -. < 'an the effi- 



:-\ for example, of the cane plant as a machine be 

 increased, or the rate a1 which tin a plant pro 



duces starch be accelerated It is true that an uncon- 

 scious attempt to do this is made in the course of 

 chemical selection, but that is oply a very indirecl 

 way of lie problem, and is not likely to 



give results as quickly as an alteration of the conditions 



uvironment. 



One of the best-known attempts that has so far 

 been made to hasten plant growth is by tin application 

 ■.it' electricity. Professor Priestley, with the assistance 

 of Sir Oliver Lodge, has in England achieved consider- 

 able success in this direction, and it has been shown in 

 a general way that there is a practical increase in the 

 yields of crops when the growing plantsare submitted 

 sontinuously to the influence ofa high tension, silent, 

 electric discharge. Previously Pollacci had obtained 

 indications that leaves can manufacture carbohydrates 

 using the carbon dioxide in the air when they are 

 traversed by an electric current, even when there is not 

 sufficient light to effect the purpose. In a later paper 

 on the subject, Priestley records the difficulty in regard 

 [Maintaining an efficient control in the open air 

 because the wind may cany the current ever from the 

 treated to the untreated area. Although the conclu- 

 sive nature of this result is thereby reduced, it is 

 nevertheless a fact that electricity dues exert an 

 appreciable stimulation on plant growth. 



Another way in which investigators have tried to 

 speed up the plant is by means of radio-active sub- 

 mces. This subject has recently received attention 

 in this journal, and it may be stated definitely that the 

 influence of these substances is beneficial, [t is only 

 a question of cost which limits the su sss of the treat- 

 ment commercially, and when radio-active by-products 

 become cheaper, there isevery possibility thai they will 

 be utilized in agriculture, The utilitarian aspect is, 

 however, not of primary importance from our present 

 point of view. In fact the criticism seems justified 

 when we say that in regard to both electrical and radio- 

 active influence, investigators tend to put the cart 

 before the horsi when commercial trials are made before 

 the physiological or purely scientific side has received 

 fuller attention. The present problem of increasing 

 the plant's efficiency Is not merely one of nutrition 

 but a problem which touches on the physical basis 

 of life. It consists in an endeavour to adjust the pro- 



perties of protoplasm to external conditions, and such an 

 endeavour requires the applicat ion of research. 



Very interesting results have ' n obtained in 



ml to the influence of shade upon assimilation. 

 The Florida work in connexion with tobacco 

 probably well known to most persons. The idea 

 originated from a chance observation that some 

 Sumatra tobacco grown near trees where it had been 

 partially shaded wasilsuperior in quality to the rest of 

 ■ho hold. Experiments were then begun to prod 

 tobacco under artificial shade. The first method of 

 shading was with latticework which produced good 

 results, bul on account ofthi cting, openly 



woven cotton cloth has replaced the lattice work. 

 A ft or a few years of successful work in Florida, the idea 

 was taken up by other States, and now growing tobacco 

 under shade is an important industry not only in the 

 United States but in South Africa, Java, and other 

 countries. It is of interest to record that this method 

 of cultivation has been tried locally in St. Kit ts with 

 highly satisfactory results. The point to boar in mind 

 in connexion with this work is that it consists in 

 producing a change in the activity of the plant cells, 

 in a re-adjustment of functions, and is on a different 

 piano altogethi r to the influence of soil nutrients. 



observations have been made in Java as to the 

 meteorological conditions obtaining under those shade 

 tents. The average temperature during the day 

 under the tents is higher and the maximum temper- 

 ature lower than in the open. The minimum 

 temperature recorded during the night was higher 

 under the tent, and the temperature of the covered soil 

 was at all times lower than on the control plots. The 

 relative humidity of the air under the tents was 

 higher than in the open, but the rainfall reaching the 

 covered soil was much less than the rainfall on. the 

 unprotected plots. 



It is probable that the absence of extreme tem- 

 peratures and the increased humidity enable the 

 stomata in the leaves to remain open longer take in 

 more carbon dioxide, bul give oul less moisture than 

 in the open. Halls work in the cotton plant, in Egypt 

 has shown that the gaseous interchange between the 

 lea\es and the air is practically arrested during the 

 hotter hours ol the day, and the results of the effect of 

 shade on tobacco tend to be m agreement. 



Still another way in which the efficiency of the 

 leaf may possibly be increased is bj a modification 



of its anatomy. A leaf by means of certain con- 

 trivances can shade itself. The writer has shown this 



