308 STIPULES LIGULA. [BOOK i. 



by comparing them with the same part differently modified 

 in neighbouring species. 



Link regards the scales of leaf-buds (called by him teg- 

 mentd) as a kind of stipule, and such they, no doubt, some- 

 times are, as in the Tulip Tree (Liriodendron) ; but then he 

 unites with them the primordial ramentaceous leaves of 

 Pinus, which have no analogy with stipules. 



De Candolle remarks, that no monocotyledonous plants 

 have stipules; but they certainly exist, at least in Naiads 

 and Arads. It is also said that they do not occur in the 

 embryo ; but then there are some exceptions to this state- 

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

 upon radical leaves, e. g. Strawberry. 



Turpin considers them of two kinds. 



1. Distinct, but rudimentary Leaves when they origi- 

 nate from the stem itself, as in Cinchonads, &c. 



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

 stalk, as in Roses, &c. 



The ligula of grasses, at the apex of their sheathing 

 petiole, a membranous appendage, which some have con- 

 sidered stipulary, should rather be considered an expansion 

 analogous to the corona of some Cloveworts (Caryophyllacese). 

 Of this the fibrous sheath at the base of the leaves of Palms, 

 called reticulum by some, may possibly be a modification. 



It has been already noted, that when stipules surround the 

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

 anterior and posterior margins are united by cohesion; a 

 property which they possess in common with all modifications 

 of leaves, and of which different instances may be pointed 

 out in Magnoliads, where the back margins only cohere, in 

 certain Cinchonads, in which the anterior margins of the 

 stipules of opposite leaves are united, and in many other 

 plants. 



3. Of Bracts. 



All the parts hitherto made the subject of inquiry are called 

 organs of vegetation ; their duty being exclusively to perform 

 the office of nutrition in the vegetable economy. Those which 



