ON LEAVES. 103 
words upon the stipula. These stipules are organs of only secondary 
importance, which accompany the leaves in certain plants. They 
are organised like leaves, but they are not true leaves. At an 
early period in the growth of certain — 
plants, two small tumours appear, one 
at either side of the base of the leaf- 2 
come stipula, a blade. They appear 
later than the leaf, at whose base they 
are developed, but at some period of their 
existence they almost invariably enclose Fig. 128.—Cells of Aquatic Plants. 
the leaf, being of quicker growth than the leaves. But their form 
and functions are altogether different, being small foliaceous 
organs with membraneous appendages, whose points of insertion are 
very various. In the Tulip-tree, Fig. 129, we observe two stipules, 
p : oe 
Fig. 129,—Stipula of Tulip-tree. : Fig. 130.—Branch of the Rose-tree, 
placed the one on the right and the other on the left of the point 
of insertion of the leaf-stalk. In the Rose-bush, Fig. 130, the two — 
Stipules are attached to the petiole of the leaf. In the Hop-plant, 
