LEVVKS. 



65 



type of the Pinnate leaf, as exliibited in the Vicia, Pea, A:c., 

 and bv the coFitinuation of the petiole we liavc thy <fm/n7,(tig. 

 54,) and hv continiiin»:oiir supposed dissection of the chestnut 

 and conceiving not only each juiniary vein as being independ- 

 ent ot'the others, but each secondary one tbiin'n^ a lamina, and 

 the priniarv vein becoming a common petiole lor thoQii >vt then 

 ^ ' ' shall have the 



type of the bu 

 pinnate leaf', as 

 exhibited in lig. 



55, 



a. We may 



conceive this di- 

 vision to go on 

 still farther and 

 form the tripirw 

 nate leaf, as in 

 the Thalictrum, 

 (tig. 55, i,) and 

 it even exceeds 

 this subdivision 

 when the term siipradecompound is applied to them, no mat- 

 ter how far the divisions may extend. The radiated 

 form of reticulated leaves, often assume the compound struc- 

 ture, as in the tEscuIus, Lupin- 

 us, Clover, &c. (tig. 56,) bu^ the 

 student will find no difficulty in 

 .yt,-^ detecting the principle on which 

 ^ thev are constructed from the 



above remarks, without a de- 

 scription. 



71. Besides the preceding 

 varieties of leaves, which may 

 be considered their common 

 forms, they often assume a variety of modifications which de- 

 serve a special attention. These variations arise from a vari- 

 ety of causes, which will be noticed under the several exam- 

 ples which we shall 

 ^^ _ adduce. A cohe- 



.d^^fcj^^^^^ glQjj jjj' parts, not 



uniVequcntly cre- 

 ates a variation 

 from the usual form. 

 The bases of the 

 upper leaves of the 

 Caprifolium Sem- 

 6* 



