14 



PLANT RELATIONS. 



ally arranged in a definite number of vortical rows. It is 

 to the advantage of the plant for these leaves to shade one 

 another as little as possible. Therefore, the narrower the 

 leaves, the more numerous may be the vertical rows (see 



Figs. 7, 8) ; and 

 the broader the 

 leaves the fewer 

 the vertical rows 

 (see Fig. 1). A 

 relation exists, 

 therefore, .be- 

 tween the breadth 

 of leaves and the 

 number of verti- 

 cal rows, and the 

 meaning of this 

 becomes plain 

 when the light-re- 

 lation is consid- 

 ered. 



18. Relation of 

 length to the dis- 

 tance between 

 leaves of the same 

 row. — The leaves 

 in a vertical row 

 may be close together or far apart. If they should be close 

 together and at the same time long, it is evident that they 

 will shade each other considerably, as the light cannot well 

 strike in between them and reach the surface of the lower 

 leaf. Therefore, the closer together the leaves of a verti- 

 cal row, the shorter are the leaves ; and the farther apart 

 the leaves of a row, the longer may they be. Short leaves 

 permit the light to strike between them even if they are 

 close together on the stem ; and long leaves permit the 

 same thing only when they are far apart on the stem. A 



Fig. 7. 



An Easter lily, showing narrow leaves and 

 numerous vertical rows. 



