CONTENTS. 
PAGE 
Summary 12 
Part I — General survey 19 
Meaning of transpiration 19 
Character of past work 20 
Outline of method principles for studying transpiration . 21 
Basis of comparison 22 
Methods of determining transpiration: 
The cobalt method 22 
Field estimates 23 
Collection of transpired water 23 
The potometer method 24 
Measuring the intake of water 24 
Loss in weight 24 
Character of plant 25 
Plant cuttings 25 
Rooted plants 25 
Summary of discussion on method principles 26 
Determining the transpiration of field crops 26 
Sources of error in potometer tests 26 
Outline of factors influencing transpiration deter- 
minations with rooted plants in pots as 
sources of experimental error 27 
Discussion of sources of error in potometer tests ... 27 
Character of potometer and contents 27 
Limitation of soil fertility 29 
Improper distribution of soil moisture 30 
Evaporation from surface of soil 30 
Entrance of rainfall 31 
Exposure of potometer to atmosphere 31 
Unintentional lack of uniformity in the soil ... 31 
Environment 32 
The plant ' 32 
Stage of maturity 33 
Errors due to methods of computation 33 
Investigators who have studied transpiration in relation 
to crop yields, based upon plants grown beyond the 
seedling stage 36 
Factors influencing transpiration in fact 38 
Outline of factors influencing transpiration in fact. 39 
