NOTES AND ABSTRACTS. 



497 



B. Sodium arsenate (65 per cent.) . . . 8oz. 

 Lead nitrate 18 oz. 



Each salt must be dissolved separately in one to two gallons of 

 water, and the lead salt added to the sodium salt, until there is a slight 

 excess of lead. The test for this excess of lead (a slight and not a large 

 excess being essential) is to dip potassium iodide paper into the mixture. 

 Excess of lead turns potassium iodide paper bright yellow. It is 

 necessary to mix the ingredients well and dilute to 25 gallons of 

 water. Wooden vessels should be used. 



Peach leaves burn very readily with lead arsenate, especially if the 

 lead arsenate is of inferior quality. 



Atmospheric conditions after spraying greatly influence the effect of 

 the spray mixture on the leaves. The final results of extensive experi- 

 ments to ascertain the exact relation between scorching and atmo- 

 spheric conditions have not yet been arrived at. 



The author has proved by experiment that the carbon dioxide of 

 the atmosphere has httle or no solvent action on the lead arsenate. 

 When the spray was applied with spring water containing various salts 

 there was an increase in scorching over the lead arsenate applied with 

 distilled water. 



Distilled water \\ith. 10 grains of sodium chloride caused serious 

 damage, while after three applications of the spray with distilled water 

 plus 10 grains of sodium carbonate peach trees were entirely defoliated. 



Lime added to the spray in the proportion of 4 lb. to 50 gallons 

 almost entirely prevented injury to the foliage. Lead arsenate does not 

 affect apple trees to any great extent.- -D. M. C. 



Leaves, Shapes of. By Prof. A. Hansgirg (Beih. Bot. Gent. 

 XXV. 1. Abt. Heft ii. pp. 137-182; 1910).— This is a condensed and 

 revised summary of the author's classification of leaf shapes. This 

 system depends upon the function or use of the leaf, and is given 

 in full in his well-known work Phyllobiologie. " 



It is impossible even to attempt to further condense the descrip- 

 tions of his fifty-five main types of leaf, especially as most of these 

 main types include several sub-types. 



In addition to the forms of the matm-e leaf Professor Hansgirg 

 briefly summarizes the adaptive characters of immature leaves, such 

 as cotyledons, and of various embryonal or " youth forms." 



He concludes that the leaves of every species of water, marsh, 

 and land plant are always in harmony with the outside factors which 

 work on them, especially with clim.atic influences, with the chemical 

 and physical constitution of the soil and with the moisture conditions. 



In most, perhaps in all plant species, there is a prevalent tendency 

 to attain the greatest possible performance (or capacity for performance) 

 by the least possible expenditure of matter and energy. 



In dealing with the extraordinary similarity in leaf structure often 

 observed in species of widely different affinity he shows that this can 

 be best explained by direct special adaptation to the particular environ- 

 ment—that is, to restricted climatic or other influences. 



