122 



ORGANOGRAPHY. 



BOOK I. 



as well as to Miquel's remark, that they never occur upon 

 radical leaves (Strawberry). 



Turpin considers them of two kinds. 



1. Distinct, but rudimentary, leaves, when they originate 

 from the stem itself, as in Cinchonaceae, &c. 



2. Leaflets of a pinnated leaf, when they adhere to the leaf- 

 stalk, as in Roses, &c. 



The li(/ula of grasses, a membranous appendage at the apex 

 of their sheathing petiole, which some have considered stipules, 

 should rather be understood as a membranous expansion 

 analogous to the corona of some Caryophylleae, such as 

 Silene. 



It has been already noted, that when they surround the 

 stem of a plant they become an ochrea ; in this case their 

 anterior and posterior margins are united by cohesion ; a 

 property that they possess in common with all modifications 

 of leaves, and of which different instances may be pointed out 

 in MagnoliaceEe, where the back margins only cohere, in cer- 

 tain Cinchonaceae, in which the anterior margins of the stipules 

 of opposite leaves are united, and in a multitude of other 

 plants. 



63 



3. Of Bracts. 



66 



All the parts that have hitherto been subjects of enquiry 

 are called organs of vegetation ; their duty being exclusively 

 to perform the nutritive parts of the vegetable economy. 

 Those wliich are about to be mentioned are called organs of 



