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PLANT PHYSIOLOGY AND ECOLOGY 



is doubtless due to the protoplasm in part, but it arises chiefly 

 from a dense or mucilaginous cell-sap. Common examples of leaf 

 succulents are the century plant, Agave, the ice-plant, Mesem- 

 hryantJiemum, and the stone-crop, Sedum, Senecio, etc. 



2. The dissected form. In these the reduction of surface is 

 brouoht about by the division of the leaf blade into narrow linear 



Fig. 51. A leaf succulent, Sedum stenopetalum. 



or thread-like lobes which are widely separated. The resulting 

 decrease in exposed surface is considerable, in some cases exceeding 

 nine tenths of the gross outline. The lobes or segments are them- 

 selves protected by a hairy covering or a thick cuticle, which is 

 often supplemented by many rows of palisade tissue, or by storage 

 tissue. Artemisia, Gilia, and Senecio contain xerophytic species 

 that are good examples of this type. 



3. The grass form. Xerophvtic grasses and sedges have narrow 

 filamentous leaves with longitudinal furrows which serve to protect 



