Plate IV. 



FIG. 16. Longisection of root, Cypripcdium pubenctns. A, B, Root-cap, com- 

 pletely covering the tip of the root; C, cent nil or plerome cylinder, showing- the 

 thin-walled procambium cells which laier develop into the elements of the fibro- 

 raacnlar bundle; D, initial group O f meristematic cells from which originates t he 

 various tissues of the i-(M)t : E, cortex developing from the peribleni of the meris- 

 tematic region at the tip of the root: F, plerome or bundle sheat h composed of a 

 single layer of modified parenchyma cells, having the walls uniformly snberi/ed 

 but folded or thickened at their points of contact; G. epidermis having its origin in 

 the dermaiogen at the apex just outside of the periblem. (x^O.) 



