126 LEAVES. 



of our common Violets, Viola cucullata> whose specific 

 name alludes to this circumstance, will serve as an ex- 

 ample. When the petiole 13 inserted into the pointed 

 extremity of a heart shaped leaf, it is said to be obcor- 

 date, as in the Wood sorrel, Fig. 42, though the equiv- 

 alent term, inversely heart-shaped, is frequently em- 

 ployed. 



A Reniform or kidney shaped leaf has a rounded ex* 

 tremity, and usually a circular excavation at its base, 

 as in Canada Snake- root and Gill. Fig. 32. 



The Crescent form, of rare occurrence, and happily 

 illustrated by a reference to the figure of the new 

 moon, may have its stem inserted into the concave or 

 opposite portion. 



The Arrow shaped or Sagittate leaf, Fig. 34, has 

 two lobes projecting from its base, one on each side of 

 the petiole to which they are nearly parallel, as in Ar- 

 row-head and Scratch -grass Polygonum sagittatum. 



The Halbert or Hastate leaf, Fig. 33, has also two 

 projecting lobes, which are nearly at right angles with 

 the leaf stalk, as in Sorrel, and Polygonum hastatum. 

 By Wildenow the Auricled leaf is regarded as a pe- 

 culiar variety of the hastate, having its lobes smaller 

 and round, but Dr. Smith speaks of them as the two 

 lateral leaflets, liable occasionally to be united to the 

 terminal one of a compound leaf. Wildenow's appli- 

 cation of the term is most usually adopted. 



A leaf is Unequal, Fig. 35, when the midrib does not 

 divide it into two equal portions. Such are the leaves 

 of the Elm and Lime trees, which last are also describ- 

 ed as Oblique. 



The leaves of a stem not unfrequently present a dif- 

 ferent form from those of the branches, and sometimes 

 they are different on the same branch or stem. The 



