72 VEGETABLE ORGANOGRAPHY. 



border of the sphincter and the pore, granules of a green 

 matter are very frequently found. 



Stomata exist in a more or less distinct manner in all 

 the foliaceous surfaces of vascular plants — viz. in leaves 

 properly so called, in stipules, in the green bark, in the 

 calyx, and pericarps which are not fleshy ; they are 

 wanting in all buds, aged stems, petioles which are not 

 foliaceous, most petals, fleshy fruits, and all seeds of 

 vascular plants ; they are also absent in all the organs 

 of cellular plants. Some naturalists, and especially 

 Treviranus, affirm however that they have seen them in 

 a small number of Mosses ; but I have never remarked 

 them. Rudolphi also denies their existence in Mosses 

 and Hepaticse. 



Leaves do not bear stomata indifferently on both sur- 

 faces : some, as for example those of the Pear, Begonia 

 spatulata, &c. have them only on the inferior surface ; 

 most liliaceous plants and grasses have them on both 

 surfaces ; in the floating leaves of the Nymphaeacea they 

 are found only on the superior surface. Rudolphi 

 affirms that they are entirely wanting in some extraordi- 

 narily woolly leaves, such as those of Marruhium. They 

 are only found on petioles when they are dilated so as 

 to form a kind of leaf, or when they are surrounded by 

 foliaceous borders. The stipules have them only when 

 they are foliaceous ; this is also the case with young- 

 shoots, which only have stomata when they are green, 

 soft, and herbaceous ; and they are generally absent when 

 they are either very woody, fleshy, or membranous ; 

 some woody stems, with a green bark of almost a foli- 

 aceous nature, have stomata as true leaves have — such 

 as, for example, those of Eiphedra. 



The involucrum and calyx follow analogous laws ; they 

 have stomata when they are foliaceous, and scarcely, if 

 ever, when they are membranous. Perigones have them 



