BRIEFER ARTICLES 



THE PHYSIOLOGICAL CONSTANTS OF PLANTS COMMONLY 

 USED IN AMERICAN BOTANICAL LABORATORIES 



The object of this paper is identical with that of its predecessor/ namely, 

 to ascertain which of the plants commonly grown or readily raised in green- 

 houses is best adapted for the demonstration of a particular physiological 

 process, and how much may be expected of it and of the others. The 

 work is being done in the Laboratory of Plant Physiology at Smith College, 

 with the advice of Professor W. F. Ganong. Others of the series are in 

 advanced preparation. 



n. EOOT PEESSUI^ AND EXUDATION 



course 



hfe of the plant, and of these osmotic root absorption is perhaps best knovm. 

 The most direct way of demonstrating the osmotic absorption and pressure 

 of the root Is by measurement of the quantity and pressure of exudation 



from 



_ I have undertaken to find for 



those greenhouse plants which are practicable for the purpose the pressure 

 of root exudation and the quantity exuded. The only work of importance 

 done upon potted plants, so far as I can find, is that of Wieler^ in 1892, 

 who recorded the pressures of some fifteen greenhouse plants, and this is 

 source of the figures in current books. Sintrle mpn^urf^m^nf<, h^vf 



been made by Detmas 



lie outside the present 



The first remii^itp fn 



: also 

 trees 



will register the pressure accurately, however small the quantity of liquid 

 exuded. Most of those used for demonstration are faulty m principle to 

 an extreme degree, as has been recently pointed out.3 After some prelimi- 

 narj' tnals I have fixed upon one which is practically that described by 

 MOESE and F£.4Ser4 for the measurement of osmotic pressures. It is a 

 men:ury rnanometer of the usual form, of o , 5-™ bore barometer tubing, 

 with a bulb blown in the middle arm. In order to test the variations in 



'Box. Gazette 40:302-305. 1905, 



PiJanzea 



♦ n.m. cnem. Jour. 

 taaicai Gazette, vol 



lood 



[5° 



