FIG. 217. Longitudinal section of Macrocystis pyrifera, showing 

 sieve-tubes, /, and sieve-plates, s, with callus (x 300). (After 

 Oliver.) 



FIG. 216. Chorda, filum Stackh. a, uppermost and lowermost portion of frond (natural size); b t 

 -transverse section, showing differentiation into cortical and epidermal layers (x 200). (After Hauck.) 



R 2 



