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W. C. Etheridge 
sheath, but extends upward, and for a part of its length it is nearly parallel 
with the stem (fig. 18). 
The non-ligulate and non-auriculate character of the leaves is a remark- 
able distinction for certain varieties of A. sativa orientalis, and is used in 
the present classification to separate such varieties from those of the same 
group having the common ligulate and auriculate leaf. The character 
has not previously been used in the classification of varieties of oats. 
THE SHEATH 
The sheath, or lower tubular part of the leaf which envelops the culm, 
offers few characteristic differences that may be used in classification. 
The differences are only in relative length and color; and, since the latter 
is subsequently discussed in relation to the color of the young plant, the 
only difference to be considered is in length. 
With respect to its length the sheath may be divided into two classes — 
those that partly cover, and those that completely cover, the internodes. 
Sheaths of the latter type are found only in varieties the leaves of which 
have no ligule nor auricle. In such varieties the sheath passes without 
apparent interruption into the leaf, and the continuous structure lies close 
to the stem to a point some distance above the node. Since in this case the 
greater length of the sheath is distinctly correlated with the more definite 
non-ligulate and non-auriculate character of the leaf, it is not in itself 
considered a specific character and is therefore not worthy of especial 
use in classification or description. 
THE CULM 
The culm, or stem, has not previously been used in classification except 
with respect to its quality, that is, its relative hardness and stiffness. 
Nilsson (1901) and Bohmer (1908-09), in characterizing groups of varieties, 
mention the quality of the culms but do not refer to their height and their 
number per plant. On the other hand, Kornicke and Werner (1885) 
mention the latter two characters in describing individual varieties, but 
do not use them in classification. The value in classification of the 
height, the number, and the quality of culms is very doubtful; for these 
characters are largely influenced by conditions of growth, and they fluc- 
tuate within a wide varietal latitude. Quality and height are also purely 
relative characters which can be judged only by comparison among many 
