xii CONTENTS 



PAGE 



Effects of a cross in normally self -fertilized species 41 



Effects of self-fertilization in normally cross-fertilized plants .... 45 



Explanation of hybrid vigor 47 



CHAPTER IV 



FIELD PLOT TECHNIC 



Soil heterogeneity ,. . .-".. . 51 



Harris' method of estimating soil heterogeneity . ........ 51 



Estimating soil heterogeneity by means of checks .....',.. 53 



Use of checks in correcting yields. . . . . . . - . -.- ~. V . . 53 



Use of probable error in eliminating strains .- . r -. \. . . 57 



The pairing method of securing a probable error . . . \ / .- . 57 



Replication and its value ." . 58 



Size of plot '.,'. . ". ..... . .\t , . 60 



Shape of plot and border effect .....!*. 61 



Competition as a factor in plot variability 62 



Climatic variations 64 



Summary of field plot technic 65 



CHAPTER V 



CONTROLLING POLLINATION * 



Selfing plants artificially 67 



Technic of crossing ....... 68 



Crossing of smal' grains '. , 69 



Crossing large-flowered legumes ..../. * . . 71 



Depollination with water 73 



Summary of technic of crossing 74 



CHAPTER VI 

 CLASSIFICATION AND INHERITANCE IN WHEAT 



Genetic classification .- . . . 75 



Wheat species groups TV... 77 



Poloni um crossed with other species 79 



Some linkage results in wheat crosses '....?-... 79 



Spike density ..;....;.... . . 81 



Seed characters . . ... . . .' v . .. .*.".' .......... 81 



Chaff characters . 84 



Presence or absence of beards 85 



Inheritance of disease resistance . ....-. 85 



Inheritance of other characters 87 



CHAPTER VII 

 CLASSIFICATION AND INHERITANCE OF SMALL GRAINS OTHER THAN WHEAT 



Classification and inheritance in oats 89 



Crosses betwen Avena fatua and A. sativa 90 



Origin of cultivated varieties of A. sterilis 90 



Differences in awn development 90 



