90 BREEDING CROP PLANTS 



CC. Lemma without teeth or awn points. 



D. Basilar connections of the grains articulate 



Avena fatua. 



DD. Basilar connections of the grains solidified. 

 E. Panicles roughly equilateral, spreading. 



Avena saliva. 

 EE. Panicles unilateral, appressed. 



Avena saliva orientalis. 



Crosses Between Avena fatua and A. sativa. It is generally 

 accepted that fatua is the stem species from which A . sativa and 

 A. sativa orientalis originated. Tschermak (1914) has made 

 extensive crosses and obtained nearly complete fertility in crosses 

 between fatua and sativa forms. Surface (1916) has found a 

 number of characters which in crosses between fatua and sativa 

 are associated with the fatua base -(1) heavy awn on lower 

 grain, (2) awn on upper grain, (3) fatua base on upper grain, (4) 

 pubescence on rachilla of lower grain and upper grain, (5) 

 pubescence on all sides of the base of lower grain and pubescence 

 on the upper grain. 



Origin of the Cultivated Varieties of A. sterilis. Norton (1907) 

 pointed out that the red oats grown in southern United States 

 without doubt descended from A. sterilis of the Mediterranean 

 region. Trabut (1914) gives quite convincing evidence that the 

 cultivated oats of the Mediterranean region have been obtained 

 from a wild A. sterilis, which is still quite common. It is of 

 interest to the student of plant breeding that the cultivated oats 

 grown in the warmer regions of the United States descended from 

 warm-climate ancestors. The value of this group of oats for the 

 southern United States has clearly been shown by Warburton 

 (1914). 



Differences in Awn Development. Varieties of oats differ 

 in the presence or absence of awns and in the degree of awn 



FIG. 21. 



1. Branch of oat panicle. 



2. Spikelet, showing tertiary floret just after blooming a, primary floret. 



3. Spikelet, showing flower parts a, outer glume; b, flowering glume; c, 

 palea; d, lodicules; e, anther; /, stigma; 0, secondary floret; h, awn. 



4. Outer parts removed, showing sexual organs. 



5. Longitudinal section ovary. 



6. Anther. 



7. Showing outer and flowering glume of lower spikelet removed a, lodicules, 

 and sexual organs. 



Size: 1, 2, about n; 3, about 2n; 4, 5, 6, greatly enlarged; 7, about 2n. 



