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(Fig. 1 C), in oUiei's, on the contrary, such ones are lacking while 

 there are bundles deeper in the bark; others again are (fuite with- 

 out bundles in the bark (Fig. 9), or, if as a rare exception bundles 

 are present, they are but very few. 



The endodermis-cells exhibit several differences ; in some species 



Fig. 3. Tiansverse sections of the axial cylinder of several Potaniogefov-specles 



(45 : 1). 



A, P. fer folia f US 



B, - coloratus 



C, - natans 



D, - in'aelongus 



E, - liicens x praehnigns 



(= P. decipiens) 



F, - gramineus X perfoliatus 



(= P. nitens) 

 The hatched parts = pith; the white parts = vascular bundles; the blacic parts 

 = mechanical tissue. Ig. channels formed hy obliteration of vessels; sg, piiloi'm. 



the cells are thin-walled and, as a rule, with distinct „Caspary"s 

 dots" ; in others the cell-walls are alike throughout and rather 

 strongly thickened: 0-Endodermis (fig. 2 D); in others, again, the 

 inner-walls and partly the radial-walls are strongly thickened, 

 while, on the contrary, the outer-walls are not thickened or but 



