513 



LECTURE x. 



i 



OP THE PETIOLE * COMPOUND LEAVES. THE SITUA- 

 TION, POSITION, INSERTION, DIRECTION, MAGNI- 

 TUDE, AND EXTENSION OF LEAVES. ANATOMY OP 

 THE LEAP. 



THE FOOTSTALK (petiolus) in every instance in 

 which it is present, constitutes a part of the leaf. 

 It is simple, in some instances, consisting of one 

 piece only, as in all simple leaves; or it is com- 

 pound (composites), consisting of one common 

 stalk divided into several distinct parts. The com- 

 mon petiole is generally termed primary (pri- 

 marius) ; the immediate divisions of this se- 

 condary ( secundarii) ; the divisions of these ter- 

 nary (ternarii), and those which support the leaf- 

 lets partial (partiales seu proprii). The petiole 

 further differs in form, in the nature of its ap- 

 pendages, its mode of insertion into the leaf, and 

 its articulations. 



In respect of form, some of the terms em- 

 ployed in the description of the stem are applicable 

 to the petiole. Thus it is said to be round (teres) ; 

 half-round (semiteres); compressed (compressus), 

 &c. according to the figure of its trans verse section. 

 The compressed petiole occasionally assumes the 



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