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MANUAL OF BOTANY 



tissue, contain ohioroplasts ; but these are relatively less 

 numerous, causing the under side of dorsi-ventral leaves to 

 appear, usually, a lighter green than the upper side. In Ferns 

 the differentiation of the mesophyll into these two layers is 



Fig. 777. 



■p.pa. 



v.b. 



— s.pa. 



St 



i.s. 



Fig. 777. Section of leaf-blade of Beta vulgaris, x 300. ep. Epidermis. 

 p.pa. Palisade parenchyma, v.b. Vascular bundle, the xylem being upper- 

 most, s.pa. Spongy parenchyma, .s/. Stoma in the lower epidermis. 

 (..*. Intercellular space communicating with stoma. 



very feebly marked. The vascular bundles are disposed between 

 the two layers of the mesophyll. 



In the iso-bilateral type there are two layers of palisade 

 parenchyma, one on each face. The spongy mesophyll is much 

 less conspicuous, and occupies the space betweeri thenj. These 



