NOTES AND ABSTRACTS. 



633 



3. The spirally-placed single leaves of the seedHng and, occasionally 

 of cone-bearing branches. 



4. Transitions between scale and fascicled leaves. 



The author describes also the conditions in fossil pines [Leptostrohus, 

 Prepinus, and Woodworthia), which practically completes the evidence, 

 in his view, for the spur shoot of Pimis being a specialized character. 



G. F. S. E. 



Plant Associations, Evaporation and Soil Moisture in. By 

 George Damon Fuller [Bot. Gaz. Iviii. pp. 193-234, Sept. 1914 ; 27 

 figs.). — On the sand dunes of Lake Michigan there is a regular 

 succession of plant associations. The cottonwood [Popidus deltoides) 

 estabhshes itself on the sand dunes, after grasses and shrubs have 

 partly overgrown them ; it is followed by first Pinus Banksiana, 

 then by black oak {Quercus velutina), oak-hickory {Q. alba) and finally, 

 by the beech-maple association. 



The authors, during 1910, 191 1, and 1912, carried out observations 

 of the rate of evaporation of the air and of the "ground-water" at 

 various stations in each of these associations. 



The results are given in graphs and tables and are of great interest, 

 showing that the evaporation rate diminishes with each change in 

 the character of the vegetation. The cottonwood is subject to sharp 

 fluctuations in the mean daily evaporation rate. These are not 

 nearly so marked in the next three associations, and in the beech-maple 

 parent conditions seem remarkably uniform. 



The differences in the amount of growth- water " which was 

 measured at 7*5 and at 2 '5 cm. depth were as follows : Beech-maple 

 100, oak-hickory 75, oak dune 29, pine dune 26, and cottonwood 

 dune 49 per cent. 



The ratios between evaporation and growth-water were 117 cotton- 

 wood dune, 107 pine dune, 9*37 oak dune, 278 oak-hickory, i'8i 

 beech-maple, and 2*91 prairie. 



The cottonwood dune is remarkable for its xerophytic character 

 and the absence of undergrowth. 



The spring vegetation of the pine dune is much more mesophytic 

 than that of summer. 



The evaporation rates and amount of growth-water in the various 

 associations vary directly with the order of their occurrence in the 

 association. 



In determining amount of growth- water weekly samples (200- 

 250 grams) of soil were taken in each association and dried at a 

 temperature of 100° C. till they reached a constant weight. The 

 evaporation was measured by Livingstone atmometers. — G. F. S. E, 



Plants, Skin Irritating. By J. H. Maiden {Agr. Gaz. N.S.W. 

 vol. XXV. p. 416). — Olearia decurrens and 0. viscidula induce dermatitis. 

 The sticky substance which covers them probably causes the irritation 

 of the skin.— S. E. W. 



VOL. XL. 



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