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 



Shoot < 



Branches 



' Blade 



Leaves 



Petiole 



Leaf-base 



Stipules 



Apex 



Margin 



Base of the blade 



Veins 



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 hes 

 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 hght 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). 



