= 
. i ‘ 
. p Frm 
The External Form of Plants. QI > 
with leaf-like expansions at the side. Some Australian 
species of Acacia possess in the early years of their life bipin- 
nate leaves with a more or less flatly expanded petiole 
(Fig. 143, 2); but subsequently the pinne are no longer 
developed, the branching is also suppressed, and the simple. 
petiole, now strongly developed into a flat plate (Fig. 143, 
a), performs all the functions of the leaf. Such a petiole is 
termed a phyMode, and is distinguished from leaves of nor- 
_ mal structure by its mode of development, as well as by its 
vertical position. ! 
At the base of the petiole on both sides are feqieaees 
found flat leaf-like appendages, the s¢zpules (Figs. 144, 145). 
Fic. 144.—Leaf of the pansy, with Fic. 145.—Leaf of the elm, with 
two large stipules. small stipules. 
These are sometimes adherent to the petiole, or adnate, as in 
the rose, and occasionaliy even run down a portion of the 
1 [The petiole of Sarracenia and Darlingtonia is expanded into a re- 
markable pitcher-like organ capable of holding a considerable amount 
of fluid. The somewhat similar pitchers of the ‘pitcher-plant’ or 
Nepenthes (Fig. 193, p. 106) are considered on the other hand to be 
expansions of the lamina, —ED. ] 
