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cutin, and as a rule, only with difficulty distinguishable from it. Cutin and 

 suberin differ chemically chiefly by the presence, in the latter only, of phellonic 

 acid and glycerol. Some botanists restrict the term cutin to the material 

 of the external cuticle and call all fatty wall materials elsewhere suberin, but 



B 



G H 



Fig. 446. — Types of endodermis. A, Diagram to show formation of 

 Caspanan band (after Priestley). B, Rammcidiis flidtam. Stem (after 

 de Bary). C, Acorus calamus. Root. D, Dryopteris filix-mas. 

 Petiole, primary state (after Priestley). E, Dryopteris filix-mas. 

 Petiole, secondary state (after Priestley). F, Iris germanica. Root. 

 G, Epidendrum sp. Root. H, Plantago major. Leaf. Longitudinal 

 aspect of Casparian band (after Trapp). 



Others limit the latter term to the material found in the cork (Latin, snher). 

 It is a matter of convention as there is no easy way of distinguishing them. 



Physiologically suberization of the cell wall cuts off the water supply of 

 the protoplasm and suberized cells thus soon die. Their walls remain, 

 however, to build up the phellem tissue. 



