ON STIPULES 



37 



which has no stipules, the petiole is always widened as 

 in the species of Helianthemum without stipules. 



This is shown, for instance, in the following figure 

 of Gistus cyprius (fig. 49). 



In Cist us vaginatus (fig. 50) the petioles are connate 

 for some distance, so as to form a sheath. 



It may, however, be objected that this is hardly a 

 case in point, because none of the species of Gistus have 

 stipules, and the petioles are all widened at the base. 



FIG. 49. SHOOT OF CISTUS CYPIUUS. Reduced one-half. 

 S, S, connate sheaths of leaves ; A, A, axillary shoots. 



There are, however, as already mentioned, some 

 other families of plants in which some species have 

 stipules and others have not. 



For instance, in the Caryoplujllacece (the Pink family), 

 the genera Spergula and Sp&rgularia have stipules, while 

 the others are exstipulate. Now Spergula and Spergu- 

 laria have narrow petioles, while in the other genera 

 Dianthus, Tunica, Gypsophila, Saponaria, Silene, Lychnis, 

 Cerastium, Arenaria, Sagina, &c. containing a very 

 large number of species, the basal part of the leaves is 



