392- 



THE STRUCTURE OF ECONOMIC PLANTS 



the cotyledonary node and into the hypocotyl; and, of these, the 

 bundles from the first pair of leaves above the cotyledons may 



Fig. ioo. A, transection of first leaf 0.9 mm. from tip where cell divisions have ceased; 

 B, transection of same leaf 0.18 mm. from tip showing meristematic activity in lamina; C, 

 transection o.i mm. from base of same leaf showing level where cell divisions have ceased; 

 D, transection through median vein of mature leaf from middle region of stem : /b, lateral 

 bundle; /^p, lower epidermis ; a«(^, median bundle; w.f/, mesophyll ; ph, phloem; r/o, stoma ; 

 uep, upper epidermis; xj i, primary xylem; xj i, secondary xylem. (After Crooks.) 



