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W. C. Etheridge 
varies with the species. In A. sterilis and its derivatives, the rhachilla 
and the callus of the upper grains are confluent, and the grains do not 
separate from their axes but tear away at its base the rhachilla itself 
(Plate I, 1, b). Among other forms, however, the rhachilla articulates 
with the callus of the upper grains approximately in the same manner as 
does the peduncle with that of the lower grain (Plate I, 2, b). 
The characteristic basilar connection of the grains is not equally retained 
by the cultivated descendants of different wild types. The cultivated 
forms of A. sterilis retain, in this respect, the character of their wild ancestor, 
the lower grain articulating with its peduncle while the upper grains 
remain strongly adherent to their rhachillas (Plate II, 1, b). But in forms 
descended from A. fatua, although the upper grains still separate easily 
from their rhachillas, the articulation of the lower grain has become so 
solidified that its lines of demarcation are completely obliterated and the 
grain separates from its peduncle only by a rupture (Plates II, 2, b, and III, 
1, b). The character of the basilar connection of their grains thus affords a 
marked distinction of cultivated A. sterilis forms on the one hand and of 
cultivated A. fatua forms (A. sativa and A. sativa orientalis) on the other. 
Trabut (1911), in studies of oats of the Mediterranean littoral, has by 
the use of this character traced a complete series of A. sterilis, beginning 
with the wild and ending with the cultivated forms. Schulz (1913), also, 
has utilized the character to distinguish A. sterilis from A. fatua, A. bar- 
bata, and A. Wiestii. Previous to the specific use of the character by 
Trabut, Norton (1907) had called attention 'to the firm union of the first 
and second grains in the spikelet of the cultivated forms of A. sterilis; 
and M. Kornicke (F. Kornicke, 1909) had communicated the result of 
certain studies by F. Kornicke in which the latter, in describing two cul- 
tivated types which he named Modigenita and Quadriflora, had mentioned 
the hanging-together of the grains during threshing — an indirect refer- 
ence to the non-articulation of the upper grains. It may readily be 
assumed that F. Kornicke's varieties were of the A. sterilis form, since 
the persistence of the upper grains to their rhachillas is limited to that 
species. 
The specific character of the basilar connection of the grains has not 
previously been utilized in extensive classification of cultivated varieties. 
Denaiffe and Sirodot (1901) have characterized various forms of grain 
bases according to the obliquity of the scar produced by removal of the 
