176 



ORGANOGRAPHY. 



the petiole where it joins the stem, but it extends downwards 

 alofig it ; in which case the stem is also termed winged, and 

 the leaf is said to be decurrent (Jigs. 260 and 353). Besides 

 the above forms of petiole, others still more remarkable occur, 

 which will be alluded to hereafter, under the head of Anomalous 

 Forms of Leaves. 



Generally speaking the petiole is less developed than the 

 lamina or blade ; it is also commonly shorter than it, and of 

 sufficient thickness to support it without bending. When it 

 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 

 Fig. 354. usually on each side of 



the petiole {fig.2ob, s,s). 

 They have the same struc- 

 ture as leaves, and are 

 liable to similar modifi- 

 cations as regards colour, 

 texture, figure, venation, 

 &c. The stipules are 

 often entirely wanting, 

 and the leaves are then 

 said to be ex.fiipulate ; 

 when present they are 

 stipulate. They are often 

 overlooked from their 

 small size ; while in other 

 cases tliey are very large, 

 as in the Pansy {fig. 

 356), and in the common 

 Pea ifig. 354). In the 

 leaves of Lotlu/rus Apha- 

 ca again {fig. 363), there 

 are no true blades to the 

 leaves, but the stipules 

 arc licre very large and 

 perform all their func- 

 tions. It sometimes hap- 

 pens that the leaflets of a 

 compound leaf ])ossess 

 little stipules of their own, 

 as in the Bean. To tliese 

 the name of stipels lias 

 been given, and the leaf 

 is then termed stipellate. 



Fig. SM. A portion of the flowering stem of 

 the common Pea, with a pinnate leaf ter- 

 minated by a tendril, and lioving two large 

 stipule!) at its biiHC, the lower margins of 

 which are dentate. 



