LEAVES AND THEIR USES 



239 



leaved plant, if one leaf 

 is on the north side of 

 the stem, the leaf next 

 above may be on the 

 south side, the next on 

 the north, and so on. 

 The leaves then are all 

 in two vertical rows, 

 and each leaf is directly 

 above the second leaf 

 below. Other alternate- 

 leaved plants have each 

 leaf directly above the 

 third leaf below ; the 

 leaves are then in three 

 vertical rows. Still 

 others have their leaves 

 in five, eight, or more 

 vertical rows. 



Whether the leaves are 

 opposite, in circles, or 

 alternate, we usually find 



Fig. 146. — The leaf mosaic of 

 a primrose. 



Fig. 145. — A plant of the wild yellow 

 lily (Lilium canadensc), whose leaves are 

 borne in circles (whorls) of four or more. 



that the result of their arrange- 

 ment is that they overlap one 

 another as little as possible. 

 If we look down on a plant 

 from above, we shall probably 

 find that the leaves are so 

 arranged that each fits in, as 

 it were, to a space left be- 

 tween the leaves above (Fig. 

 146), so that each receives the 

 greatest possible amount of 

 light. The appearance is 

 much like that of a mosaic 

 floor, in which each angular 



