THE PARTS OF A FLOWERING PLANT 13 
17. The Shoot. As stated above, the shoot is composed 
of a branched or an unbranched stem, usually, but not 
always, bearing leaves (Figs, i and 57). The leaves are 
commonly composed of a flat, expanded, and usually 
green part (the blade}, which may or may not be borne 
on a leaf-stalk (petiole}. The portion of the leaf attached 
to the stem is the leaf-base, the edge of the blade is the 
margin, the tip of the blade is the apex, and the portion 
of the blade attached to the petiole is the base of the blade 
(Fig. 6). These parts may be tabulated as follows: 
f Stem 
Branches 
Shoot 
Blade Margin 
Petiole 
Leaves \ _ . - , 
Leaf-base 
Apex 
Base of the blade 
Veins 
[ Stipules 
The main functions of leaves are: (i) to elaborate plant 
food in the presence of sunlight; (2) to help regulate the 
water content of the plant. In these two functions lies 
the significance of the fact that the leaf-blade is flat, 
expanded, thin, and green. This will be explained in 
Chapters IV and VII. Leaves also have other important 
functions, to be mentioned later. 
The branches serve to support the leaves, to hold them 
up into the light and air, and to connect them with the 
root-system. 
18. The Flower. The interpretation of the flower is 
not essential at this point, and is reserved for a future 
chapter (Chapter XXIX), when it may be better under- 
stood. It is sufficient here to state that the chief function 
of the flower is the production of seed. 
The essential parts of a flowering plant are shown in 
the diagram (Fig. 7). 
