CONTENTS. 



Department Bulletin No. 842. — The Nematode Disease of Wheat Caused, 



by Tylenchus Tritici — Continued. Page. 



Host plants 28 



Methods of spreading the parasites ,>, 30 



Methods of control 32 



Summary , 35 



Literature cited 38 



Department Bulletin No. 843. — The Bean Ladybird: 



Introduction 



Synonymy - 2 



Description 2 



Distribution 5 



Danger of future spread 5 



Life history and habits 7 



History and literature 10 



Unpublished records 11 



Natural control 13 



Preventive measures 15 



Direct measures of control 16 



General summary 18 



Literature cited 20 



The bean ladybird in Colorado in 1919 21 



Department Bulletin No. 844. — Sweet-clover Seed: 



Part I. — Pollination studies of seed production — 



Unsatisfactory yields of sweet-clover seed 1 



Previous investigations of the pollination of sweet clover 2 



Outline of pollinating experiments 3 



Structure of the flowers of Melilotus alba 4 



Development of the floral organs of sweet clover 5 



Fertilization in Melilotus alba 8 



Development of the seed 8 



Mature pollen of sweet clover 9 



Germination of the pollen 9 



Cross-pollination and self-pollination of sweet clover 10 



Artificial manipulation of sweet clover flowers 10 



Seed production of Melilotus alba under ordinary field conditions 13 



Efficiency of certain kinds of insects as pollinators of sweet clover 14 



Relation of the position of the flowers on Melilotus alba plants to seed 



production 19 



Influence of the weather at blossoming time upon seed production. . . 20 



Insect pollinators of sweet clover 21 



■ Effect of moisture upon the production of Melilotus alba seed 22 



Part II. — Structure and chemical nature of the seed coat and its relation 

 to impermeable seeds of sweet clover — 



Historical summary '. 26 



Material methods 30 



Structure of the seed coat 31 



Microchemistry of the seed coat , .-.-.--. 33 



The seed coat in relation to the absorption of water 34 



A comparison of permeable and impermeable seed coats 34 



The action of sulphuric acid on the coats of impermeable seeds 35 



Literature cited 37 



Department Bulletin No. 845. — Production of Lumber, Lath, and 

 Shingles in 1918: 



Introduction 1 



Total lumber production 2 



Lumber production by classes of mills 3 



Lumber production by States 12 



Lumber production by kinds of wood 15 



Yellow pine 19 



Douglas fir 20 



White pine 20 



Oak 21 



Hemlock 22 



