EFFECT OF SPRA YING BORDEAUX MIXTURE ON FOLIAGE. 



somewhat unsatisfactory ; yet there is 

 sufficient data to indicate a gain from 

 spraying and an additional increase of 

 thickness where an excess of lime was 

 used. 



These experiments conducted in the 

 greenhouses, where most of the condi- 

 tions were under control, give f)erhaps 

 more valuable results than if they had 

 been carried on in the open air, as rain 

 and other atmospheric disturbances 

 which would affect the plants, were en- 

 tirely avoided. A steady temperature, 

 a regular supply of water, without wash- 

 ing the leaves an even spraying of the 

 leaves with an atomizer, all went to se- 

 cure uniformity of surrounding influ- 

 ences. On the other hand, the dews, 

 which are deposited on outdoor plants, 

 might have the effect of bringing into 

 solution some of the compounds of the 

 dried residue of the mixture adhering to 

 the leaves. 



The results, on the whole, confirm 

 Lo jemann's statements, that the increas- 

 ed thickness of the leaf resulted from 

 spraying with Bordeaux mixture, and 

 that the thickness was probably due to 

 an increase in the length of the palisade 

 cells. 



Lodemann's measurements, however, 

 are manifestly wrong, as the plum leaves 

 examined by him are stated to be " from 

 10.4 to i2.9micromillimetres in width," 

 or about the same width as length of a 

 good-sized microbe. Leaves would be 

 very flimsy structures if this were the 

 case. 



With regard to the increased greenness 

 of the' foliage, it is well-known that cal- 

 cium is especially abundant in the 

 leaves of green plants, and it is probable 

 that some of the calcium of the lime in 

 the Bordeaux mixture is absorbed by 



the leaves. Boussingault found that if 

 calcium sulphate be placed on the 

 leaves of a plant it will disappear in a 

 few hours, and sooner on the lower than 

 on the upper surface. Further, the 

 effect of depriving plants of calcium as 

 an ingredient of their food supply is well 

 shown in the text books on Physiological 

 Botany. Hence it is not improbable 

 that the increased greenness in the 

 leaves sprayed with an excess of lime, is 

 caused by the leaves absorbing an ex- 

 cess of calcium. 



CONCLUSIONS. 



Bordeaux mixture has an invigorating 

 effect on leaves, as evidenced by the 

 increased thickness and the marked de- 

 velopment of the chlorophyll granules 

 in the cells. This increased vigor is of 

 much importance, as a strong healthy 

 plant is always in a much better condi- 

 tion to withstand the attacks of fungus 

 diseases than a weakly one. 



Instances of losses from improperly 

 made Bordeaux mixture indicate that a 

 lack of sufficient lime may result in in- 

 jury. Crumpling of the leaf resulted in 

 Nos. two and four from lack of sufficient 

 lime. 



An excess of lime gave better results 

 than smaller amounts. The leaves seem 

 able to take up some of the lime ; and 

 additional lime give the foliage increased 

 vigor. Hence, it might be advisable to 

 use larger amounts of lime than are 

 generally used in the mixture. The in- 

 creased thickness of the leaf is probably 

 due to the increased development of 

 the palisade layers of cells. 



F. C. Harrison, 



Bacteriologist. 



O.A.C. Guelph. 



