THE LEAF. 



53 



woody Dicotyledons there is generally a little protuberance under 

 the cicatrix, which is termed the pidvlnus. In Monocotyledons 

 the cicatrix is usually very broad, from the base of the petiole em- 

 bracing the stem widely. In some cases the petiole is not regularly 

 disarticulated, but withers down ; but then the decay generally termi- 

 nates at a definite point a little above the base, leaving a portion of 

 the latter in the form of a scale-like or tooth-like process projecting 

 from the stem. 



Tooth-like processes left by the decay of the petioles may be seen on 

 the underground stem of the common Primrose &c., and on the trunks of 

 certain Palms. 



Stipules. The stipules or leaf-like append- Fig. 63. 



ages of the petiole usually stand at the base of 

 the petiole, one on each side, free or adherent 

 to it (fig. 63). The free leafy stipules are 

 sometimes highly developed, and in Lathyrus 

 Aphaca they exercise the functions of the blade, 

 the leaves of this plant consisting merely of a 

 petiole destitute of a lamina. TV hen the mar- 

 gins of the stipules next the petiole are con- 

 tinuous with that organ, forming as it were 

 wings to it (Rosa), they are called adnate (fig. 64). They are also 

 often united by their margins independently of the petiole, or, in 

 other words, are not separated from each other (connate) : thus in 

 the Plane tree and in Astragalus they are united by the outer mar- 



Leaf of Lotus with free 

 stipules. 





Fig. 64. 



Fig. 65. 



Compound (pinnate) leaf of the Rose, 

 with adnate stipules. 



Ocrea of Polygonum. 



gins (turned away from the petiole) so as to form a kind of leaflet 

 on the opposite side of the stem (intrapetiolar) in Potamoyeton 



