THE STOMATA. 73 



almost entirely on their lower surface, even when they 

 are coloured, as in the Marv-el of Peru (Mirahilis), 

 and they are most frequently wanting on the superior 

 surface ; they are very rarely found in the petals, except 

 in some plants, such as Michauxia, Campanula har- 

 hata, Peganum harmala, which have them externally ; 

 Dictamnus albiis, and, according to Rudolphi, Epilohium 

 angustifolium, present them on both surfaces. I have 

 found them on the inferior surface of petals, which have 

 been transformed into leaves, in a monstrosity of Ranun- 

 culus philonotu. I have never seen them on the styles 

 or stamens ; but Rudolphi asserts that they exist on 

 some, such as those of Lilium hulhiferum. They are 

 often found on pericarps which are of a foliaceous 

 nature ; but all that are fleshy are, without exception, 

 devoid of them. 



This last law is analogous to that which is observed in 

 leaves ; those which are fleshy have much fewer, in pro- 

 portion, than those of a thin or fibrous texture. In all 

 these difierent organs we never find stomata, either on 

 the primary or secondary veins, or on their ramifica- 

 tions, but always on the parenchyma properly so called. 

 Tliis position of the stomata is contrary to that of the 

 hairs, which spring from the veins or their ramifica- 

 tions. 



The stomata are, in general, scattered over the 

 parenchyma, and distributed at nearly equal distances; 

 sometimes, as is seen in leaves with parallel veins, they 

 are disposed in one or two longitudinal rows between the 

 veins. Those of the Equisetum, observed by Vaucher, 

 are disposed upon the stem in longitudinal lines, between 

 the projecting veins ; their number and disposition 

 would even furnish crood soecific characters. 



There are some leaves where they are found congre- 

 gated here and there, forming kinds of little rosettes or 



