STUDIES IN SOIL PHYSICS 



By E. E. FREE 



Scientist. Bureau of Soils, 

 U. S. Department of Agriculture 



This series o. papers, which appeared in The Plant World during 



1911, has been revised by the author and is now 



oTered in durable pamphlet form 



Single copies $ .75 Five copies S3.00 



This book is the most recent, informing, and suggestive treatment of 



a field of study which is of vital importance rn botany, 



agriculture, and forestry. 



PLACE IT IN THE HANDS OF YOUR STUDENTS 



THE PLANT WORLD TUCSON, ARIZONA 



Automatic Transpiration Apparatus 



The apparatus devised by Dr. E. N. Transeau for the graphic recording of 

 transpiration rate has been placed in our hands for sale. This apparatus was 

 described and illustrated in Botanical Gazette, Vol. 52. pp. 54-60. 



Full particulars and prices on application. 



THE PLANT WORLD, TUCSON, ARIZONA 



Special Clearance Sale of Back Numbers 



Five back numbers of The Plant World, of our own choosing, will be sent post 

 free for 60 cents. Our regular price would be SI. 50. The issues available for 

 this offer are generously illustrated, and especially rich in articles on plant 

 geography, ecological botany, and travels, not to mention a wide range of 

 other subjects. Any preference of the purchaser for particular numbers, or 

 for a particular class of articles, will be honored as far as possible. 



THE PLANT WORLD, TUCSON, ARIZONA 



