LEA VES 



153 



Petioles. The petioles of leaves vary greatly in length, 

 width, color and outline. The length and width of the petiole 

 vary in every species of plant, but in each the maximum 

 length is fairly constant. The color of the petiole varies in 



FIG. 90. Attachment of Petiole to Blade. 1, Stoneroot (Collinsonia 

 canadensis) normal attachment; 2, nasturtium (Tropceolum majus); 3, 

 mandrake (Podophylum peltatum) peltate attachment. 



different plants, being like the blade, more highly colored in 

 spring and autumn. The outline of sections of the petiole 

 may be circular, rectangular, oval, etc. 



If the upper surface of the petiole is sunken below the 



