THE STEM AND THE LEAF 



59 



light, as they are either narrowed at the base or borne on long 

 leafstalks, so that they do not overlap and shade each other at 

 the bases. The leaves of the century plant are broad at the base, 



Fig. 44. Leaf mosaic ot a begonia 

 The leaves are so disposed that little shading of one leaf by another occurs 



but this portion is pale and much thickened and does hardly 

 any photosynthetic work, serviag rather as a storehouse for 

 plant food. At floweriag time this food is removed, the leaves 

 droop, and after the seeds are ripe the leaves die (Fig. 63). 



Fig. 45. Mosaic formed by leaves of unequal size 

 Top view of a branch of deadly nightshade. After Kerner 



56. Leaf mosaics. Any combination of leaves, whether 

 found ui rosette plants or on longer stems, in which the space 

 is very fully occupied by leaves, with few spaces horizontally 

 between them, is called a leaf mosaic (Figs. 44 and 45). Walls 



