66 MORPHOLOGY. 
a broad sheath (vaginw), and surrounds the stem in a tube-like 
form. With the leaf-sheath are also to be classed the stipules 
(stipule),’ which are mostly of different, but occasionally of 
the same form and color as the main leaves (Asperula), and oc- 
cur at the base of the latter. 
The form of leaves is very multifarious, although those which 
are. developed in a broad, flat form decidedly predominate. 
If one and the same plant possesses differently formed leaves 
at different places, it is called heterophyllous* (Eucalyptus, 
Fig. 2). Since the leaves serve principally for the assimilation 
of carbonic acid in the light, they present their broad, green 
surfaces to the sun. This applies, however, only to the true 
<< 
MIDNA FAG 
Fig. 3.—Rhizome of ‘Gratiola officinalis, with roots. a—b, rhizome; at 6, the ter- 
minal bud; d, under or rudimentary leaf; c, a shoot issuing from the axil of a rudimen- 
tary leaf, and likewise provided with rudimentary leaves, 
FoLIaGe LEAVES (Folia), which are chiefly met with in the 
region between the root and the flower. It is otherwise with the 
_ UNDER-LEAVES or CATAPHYLLA (squame):, which are inserted 
chiefly on the basal portion of the stem, and on the rhizomes, 
stolons, etc., with a broad surface (Fig. 3). They are for the 
most part brownish or pale in color, and to be regarded as 
protecting envelopes for the tender, growing portions. The 
fleshy bulb-scales are likewise rudimentary or under-leaves 
’ 1 Properly halm or straw, on account of their dry, membranous con- 
sistence. In German, Nebenblitter. 
*”Erepos the other, and puAAor leaf. 
5 Squama, scale. 
