548 ECOLOGY 



leaves toward light; in so far as the upper surface, regardless of exposure, 

 has the maximum chlorenchyma development, the advantage is evi- 



FlG. 786. A plant (Nicotiana alata), illustrating a conical habit due to a decrease 

 in the size and in the horizontally of the leaf blades from the base to the apex ; note also 

 that the leaves change in shape, being blunt below and pointed above, and that they are 

 arranged in many vertical rows; this plant, like the mullein, illustrates a relative maxi- 

 mum of lighting coupled with a minimum of shading, and also a progressive increase 

 from the base to the apex of features that protect from excessive transpiration. Pho- 

 tograph by FULLER. 



dent, but in a great many leaves (as in Lactuca scariola, Populus 

 deltoides, and Eucalyptus globulus), the greatest development of the 



