1908] FREEMAN—DETERMINATION OF TRANSPIRATION 129 
the plant. While in my method normal air is supplied, both of the 
above investigators first completely dried the air before allowing 
it to reach the plant. This is detrimental, for as BURGERSTEIN® 
says: “In Gegensatze zur zweiten hat die dritte Methode, bei welcher 
die evaporierte Wassermenge aus der Gewichtszunahme hygroskop- 
ische Substanzen in Erfahrung gebracht wird, den Nachteil das sich 
die Pflanze in einer zu trockenen Luft befindet.” 
SUMMARY 
1. In plant breeding and in physiological and ecological work, 
it is very necessary to have some accurate and practical method of 
measuring the transpiration of plants. 
2. The potometer method does not give the normal transpiration 
rate of a plant, neither can it be depended upon to give a rate which 
's even comparative as between different plants. 
3- By the method herein described the transpiration of a plant 
under known and constant conditions may be accurately measured. 
4. It is possible by this method to demonstrate individual differ- 
€nces in the transpiration rates in different plants of the same species. 
5: By the use of this apparatus, data may be secured to serve as a 
basis for plant selection and breeding. 
MANHATTAN, Kansas 
3 ; ery 
BURGERSTEIN, ALFRED, Die Transpiration der Pflanzen 12. 1004. 
