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BOTANICAL GAZETTE 



ith the long-known forms, are the simple 

 s. The author concludes that there is no 

 evidence of any connection between Bennettitales and angiosperms— J. M. C. 



Atmometry and the porous cup.— With the increasing attention now being 

 given to the quantitative determination of ecological factors, it is fortunate 

 to have the technique of one of the most fruitful fields of investigation reviewed 

 and summarized by the worker most prominently connected with it from the 

 beginning. Such a review of the instruments and methods of measuring the 

 evaporating power of the air by Livingston' 2 has recently appeared, including 

 descriptions of the various forms of atmometers and their operation and 

 standardization. Prominent among the recent improvements in this field 

 is the rotating table for standardizing the porous cups, already noted in this 

 journal," and the improved form of the non-absorbing porous atmometer 

 devised by Shive^ to provide against errors caused by the absorption of water 

 by the atmometer during rainfall. The various difficulties encountered by 

 Livingston and other workers during the ten years since he invented the 

 present form of porous cups are discussed in a way that makes the work 

 invaluable to all workers in this field.— Geo. D. Fuller. 



Evaporation in a marsh.— In a marsh upon the borders of Lake Erie, where 



the different associations for a period of four weeks following June 29, and 

 found the highest rate above the open water in the Scirpus association, with the 

 lowest in one dominated by Calamagrostis canadensis. The comparative 

 values for associations dominated by Calamagrostis, Typha, Phragmites, 

 Pontederia, Sparganium, Castalia, and Scirpus are correspondingly 100, 102, 

 113, 125, 137, 343, and 413. It is to be regretted that the observations did 

 not extend over a longer period, and that Sears has not reduced his results 

 to the unit commonly used by other workers in this field, that is, to loss per 

 day from the standard atmometer. However, it is an important addition to the 

 data now gradually accumulating of the evaporating power of the air in various 

 habitats.— Geo. D. Fuller. 



Rachiopteris — Miss Bancroft' 6 describes a large amount of material 

 from various sources, which is referred to Rachiopteris cylindrica. Two types 



"Shive, J. W., An improved non-absorbing porous cup atmometer. Plar 

 ■rid 18:7-10. 1915. 



» Sears, P. B., Evaporation and plant zones in the Cedar Point marsh. Ohi 

 ir.Sci. 16:91-100.^.5- 1916. 

 ' 6 Bancroft, N., Contributions to our knowledge of Rachiopteris cylindrica Wil 



