PnTATTXTr TADTtr FOR equalizing the exposure 

 IvU 1 A 1 1 IMj 1 1\IjLlj of a series of plants ^j? ^ 



This becomes an indispensable de- 

 vice in every physiological laboratory 

 after its first trial. It is impossible to 

 give equal conditions to all plants in a 

 standing series of cultures. For the 

 proper standardization of Atmometer 

 Cups it has been found absolutely nec- 

 essary. The table-top is circular, 4 feet 

 in diameter, of 5-ply wood, and is 

 mounted on a bicj^cle wheel, which is 

 supported on a heavy iron tripod base. 

 It is rotated by a belt from a reducing 

 gear, which is operated by a 1/20 H. P. electric motor or other sources of 

 power, A hot-air engine or small gas engine would also serve. A good speed 

 of ro.tation for most purposes is from 1/5 to 5 revolutions per minute. See Plant 

 World 15: 157-162, 1912; Physiological Researches 1 : 345- 1915. 



WEIGHT READY FOR SHIPMENT, ABOUT 150 LBS. 



Price of Rotating Table Complete, $35.00 

 Table Top Alone, $8.50 Tripod Base Alone, $12.50 



THE PLANT WORLD 



TUCSON, ARIZONA 



SPHERICAL ATMOMETER CUPS 



A spherical evaporating surface, 5 cm. 

 in diameter, presenting the same external ex- 

 posure in all directions, with glazed cylindri- 

 cal neck 3 cm. long and 2 cm. inside diameter. 

 They are composed of very resistant material, 

 of proper porosity for atmometric work, and 

 are to be mounted on rubber stoppers as in 

 the case of cylindrical cups. The spheres may be cleaned with brush and distilled 

 water, may be treated with acid, and even heated to red heat. They should thus be 

 capable of many years of use, without permanent alteration of the coefficient. They 

 are not easily broken. 



These new spheres are supplied either standardized or unstandardized. Stand- 

 ardization is carried out with reference to a newly adopted spherical standard; spheres 

 cannot be satisfactorily standardized to the cylindrical standard cup. Therefore 

 readings from spheres are not satisfactorily reducible to terms of readings from cylin- 

 ders (see Plant World, Vol. 18, pp. 21, 51, 95, 143). 



Unstandardized White Spheres, $2.25 each, $20.00 per ten 

 Standardized White Spheres, $2.75 each, $25.00 per ten 



THE PLANT WORLD 



TUCSON, ARIZONA 



