A Study of Variability in the Burt Oat 
Plate 1 
A to C.—Spikelet disarticulation, or separation of the lower floret from the basal segment of the rachilla. 
A.—Disarticulation by abscission, the method occurring commonly in the wild oat species Avena fatua 
and A. sterilis, and in some strains of the Burt oat. B—Disarticulation by semiabscission, more or less 
intermediate between A and C, apparently resulting partly from abscission and partly from fracture, and 
leaving only a slight and often poorly developed cavity in the base of the lemma. C.—Disarticulation 
by fracture. The method of separation most characteristic of the cultivated varieties of Avena sativa, 
resulting in a rough, fractured tissue with no observable cavity at the base of the lemma. 
D to F.—Floret disjunction, or separation of the second floret from the first or lower floret. D.—Dis¬ 
junction by disarticulation. The second floret disjoins by disarticulation of the second rachilla segment 
from the base of the second floret, the common method in the wild species Avena fatua and the cultivated 
varieties of its derivative, .4. sativa. E—Disjunction by heterofracture. The rachilla segment breaks 
transversely somewhere in the middle portion, or may break both transversely and longitudinally, the 
latter splitting being very diverse. F—Disjunction by basifracture. The common method of separation 
in the wild Avena sterilis and the cultivated varieties of its derivative, A. byzantina, the rachilla segment 
'breaking at or near its base and remaining firmly attached to the base of the floret. 
