;i7o 



ORGANOGRAPHY. 



Fig. 351. 



Generally speaking the 

 petiole is less developed 

 than the lamina ; it is also 

 commonly shorter than it, 

 and of sufficient thickness 

 to support it without bend- 

 ing. When the petiole 

 is very long or thin, or 

 when the lamina is very 

 heavy, and in other cases, 

 it becomes more or less 

 bent downwards towards 

 the earth, and no longer 

 supports the lamina in a 

 horizontal direction. 



6. STIPULES. 



Stipules are small leafy 

 bodies situated at the base 

 and usually on each side 

 of the petiole {fig. 248, 

 s, s). They have the same 

 structure as the blades of 

 leaves, and are liable to 

 similar modifications as 

 regards venation, outline, 

 margin, &c. The sti- 

 pules are often entirely 



„. „ , . ^. , ., « , . , wanting, and the leaves 

 Fuj. 351. A portion of the flowering stem of .i -1^1 j.- 



the common Pea, with a pinnate leaf ter- are then said to be exstt- 



miuated hy a tendril, and having two large pulate: when present the 



stipules at its hase, the lower margins of i -• 7 ^ m 



which are dentate. l.ea.ves a.ve sUpiUafe. lliey 



are often overlooked from 

 their small size ; while in other cases they are very large, as 

 in the Pansy (fig. 353), and in the common Pea {fig. 351). 

 In the leaves of Lathyrus Aphaca again {fig. 360), there are no 

 true blades, but the stipules are here very large and perform 

 all their functions. It sometimes happens that the leaflets of a 

 compound leaf possess little stipules of their own, as in the Bean 

 and Bladder-Nut ; to these the name of stipels has been given, 

 and the leaf is then termed stipellate. 



Stipules either remain attached as long as the leaf, when they 

 are said to be 2^(^^sistcnt ; or they fall off soon after its expan- 

 sion, in which case they are deciduous. In the Beech, the Fig, 

 the Magnolia, &c., they form the tegmenta or protective coverings 

 of the buds, and fall off as these open (see page 93), 



The stipules vary in their position with regard to the petiole 

 and to each other, and have received different names accord- 



