VI 
CIRCULARS OF THE BUREAU OF PLANT INDUSTRY. 
Page. 
Circular No. 12. — Dry-Land Grains — Continued. 
The great wheat groups — Continued. 
The hard winter or Crimean wheats 10 
Intermountain wheats 11 
Greater uniformity necessary 12 
The Pacific wheats 12 
Future improvement 13 
Conclusions 14 
Circular No. 13. — The Work of the San Antonio Experiment Farm in 
1907. 
Introduction 3 
Lines of work undertaken 4 
Tillage experiments 4 
Deep plowing and subsoiling 4 
Early fall plowing 5 
Manuring 5 
The dust mulch 6 
Winter tillage 7 
Rotation of crops 7 
Methods of preventing sterility in sorghum 9 
Eradication of Johnson grass 9 
Crops for forage and green manure 11 
Crops raised for grain 13 
Cultural experiments with cotton 13 
Acclimatization of weevil-resisting types of cotton 14 
Horticultural work 14 
Conclusions 15 
Circular No. 14. — Change of Vegetation on the South Texas Prairies. 
Circular No. 15. — The Fertilizing Value of Hairy Vetch for Connect- 
icut Tobacco Fields. 
Introduction ' 1 
Adaptability of hairy vetch to tobacco fields 1 
Importance of inoculating hairy vetch 2 
Pot experiments with hairy vetch 2 
Nitrogen furnished by hairy vetch turned under 3 
Pot experiments with tobacco 4 
Conclusions 5 
Circular No. 16. —A New Basis for Barley Valuation and Improve- 
ment. 
Circular No. 17. — Index to Papers Relating to Plant-Industry Sub- 
jects in the Yearbooks of the United States Department of Agricul- 
ture. 
Explanati try statement 
1 1 idc \ 
Circular No. 18. — Reappearance oi a Primitive Character in Cottou 
Hybrids. 
Introduction 
Primitive characters shown in reversion and recapitulation 
