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W. C. Etheridge 
bill, although between varieties of a similar type the leaves are scarcely 
unlike. The varietal difference in size of the leaves is better expressed 
in width than in length, for the latter dimension is 
the less constant in a given variety and, because of 
the drying and breaking of the tips, is often difficult 
to ascertain correctly. However, the dimensions of 
the leaves are not here used in classification, but 
merely as a minor character in description. The only 
important character of the leaf used in this classi- 
fication is the presence or the absence of its cilia, 
or marginal hairs (fig. 16). The cilia, when present, 
are to be found on the margins of all leaves below the 
uppermost one, and they 
are a definite, inherited, 
and easily observed mor- 
A B phological character, 
Fig. 16. sections of sometimes useful in dis- 
OATS LEAF SHOWING , • • i • • , • 
(a) glabrous mar- languishing varieties. 
gins and (b) cili- They are best observed 
ATE MARGINS * 
in the green plant, tor 
when at maturity the leaves become shriv- 
eled the cilia are obscure. 
THE LIGTJLE AND THE AURICLE 
The ligule, a scarious, cartilaginous append- 
age borne at the orifice- of the sheath, is 
characteristic of the Gramineae and is rarely 
wanting (fig. 17). Indeed the ligule is such 
a fixed and definite morphological character 
of the grass family that its structural vari- 
ation and its absolute length are frequently 
used by botanists as a feature in the char- 
acterization of separate species. Within 
species of the Gramineae, the absence of 
the ligule is so distinctly unusual that it is 
of remarkable value for fixing the identity of a single variety or of a group 
of varieties. 
A NORMAL LIGULATE AND 
AURICULATE LEAF 
A, Leaf bending away from the stem 
at its junction with the sheath; B, sec- 
tion of leaf showing on the inner side 
the ligule 
