December, 1908.] 



553 



Plant Sanitation. 



air sprayer. That is, the air is pumped 

 into the tank until sufficient pressure is 

 obtained, and the spray mixture is 

 forced through the nozzle until the air 

 pressure is entirely reduced. By careful 

 trial, the amount of spray material in 

 the cylinder and the amount of pressure 

 may be so adjusted, that one pumping 

 will serve to force out all the spray 

 mixture. 



In this connection, another disadvan- 

 tage ia the use of lead arsenate is likely 

 to be noticed. This material is very 

 heavy, and a considerable amount of 

 agitation is necessary to prevent the 

 poison from settling to the bottom of 

 the sprayer and thus producing an 

 unequal distribution. Whether it will 

 be possible to get the labourers to , 

 agitate the mixture sufficiently by shak- 

 ing the sprayer as they walk, so that 

 the poison may be equally distributed 

 throughout the entire operation of 

 spraying, I'emahis to be seen. The fact, 

 however, that good results in the use of 

 lead arsenate have already been obtained 

 at Barbados, would seem to indicate 

 that this is not an insurmountable 

 obstacle. 



One of the points of comparison 

 between dusting and spraying has re- 

 ference to the weights of the materials 

 used. In dusting with Paris green and 

 lime at the rate of one to six, it will be 

 seen that in applying each pound of the 

 poison, a total of 7 lb. of material has to 

 be handled by the labourers, while in 

 spraying at the rate of 1 lb. of lead 

 arsenate to 100 gallons of water, the 

 material used will have a total Aveight 

 of nearly 1,000 lb. These figures may be 

 taken to represent the amounts used per 

 acre per application. 



In addition to this, the value and 

 weight of the respective apparatus used 

 in the application of the spray and of 

 the dust are to be taken into consider- 

 ation. The cloth bag used in the applica- 

 tion of Paris green costs only a few cents 

 and has very little weight, while each 

 sprayer weierhs several pounds, and 

 represents an initial cost of several 

 dollars. 



Paris green usually costs slightly more 

 per pound than lead arsenate, but since 

 it is customary to use a little more of 

 the latter substance than of Paris green, 

 the difference in the first cost of the 

 two materials is very small. If, how- 

 ever, the lead aresnate proves, as is 

 expected, to be much more adhesive 

 than Paris green, the saving of several 

 applications, and the more continuous 

 protection to the plants, due to the 

 70 



lasting properties of the lead arsenate, 

 may make this a much cheaper insecticide 

 in the long run. 



It may be added that during the 

 present season one firm of manufactur- 

 ing chemists in the United States has 

 succeeded in producing a good grade 

 of lead arsenate in a dry powdered 

 form. This has been tried by the Crop 

 Pest Commission of the State of Louisiana 

 in certain of their experiments and the 

 results are very promising. A small 

 quantity of this material will be imported 

 by the Imperial Department of Agricu- 

 ture for trial.— Agricultural News, Sep- 

 tember 19, 1908. 



PLANT PATHOLOGY IN ITS RELA- 

 TION TO OTHER SCIENCES. 



In the naming of this association of 

 scientists, the Illinois Academy of 

 Science, there was recognized a very 

 subtle tendency in advancing civilization 

 and modern educational thought. It 

 has often been noted that as civilization 

 becomes more highly developed, it also 

 becomes more complicated, and men 

 become more independent upon one 

 another. So, too, as knowledge increases 

 in volume and in extent, the fields of 

 study which were formerly quite in- 

 dependent grow closer together, and 

 new fields opening up, find themselves 

 involved with many others already 

 existing. We are finding, in fact, that 

 knowledge is a unit — not a mere assem- 

 blage of disconnected ideas, so that it is 

 advantageous, now and then, to examine 

 a new science, and to discover, in so far 

 as we cam with what other parts of the 

 body of science it may be intimately 

 related. Therefore, it has seemed advis- 

 able to consider, how plant pathology is 

 related to other sciences. 



Plant pathology is one of the youngest, 

 and perhaps one of the least understood, 

 of the recently developed sciences. When 

 considered in its broadest meaning, it is 

 for plants, as medical science is for man, 

 a study of the normal, and of the diseased 

 conditions of the organisms. In the 

 narrower and more widely accepted 

 sense, however, it deals with the abnor- 

 malities both of form and of function, 

 which in animals are, and in plants may 

 be, called diseases. There is one other 

 phase also which must always appear, 

 that of the prevention and the cure of 

 the maladies. 



Few people who have not studied the 

 matter realise the very large loss of 

 money occasioned each year by these 

 plant diseases, and fewer yet know that 

 much has already been done to diminish 



