Contents 



Pa&e 



Introduction 1 



Bibliography 1 



Appendix 30 



Subject index 31 



Author index 31 



Trade names are used in this publication solely for the purpose of providing 

 specific information. Mention of a trade name does not constitute a guarantee or 

 warranty of the product by the U.S. Department of Agriculture or an endorse- 

 ment by the Department over other products not mentioned. 



FOLLOW THE LABEL 



Washington, D.C. 



Issued December 1968 



IV 



