214 



BOTANICAL GAZETTE 



[SEPTEMBER 



than spiral. Since neither transverse nor radial preparations show- 

 crushed masses of cellular material at the centripetal ends of 

 bundles, there can be no doubt that the xylem elements which 

 can be seen to terminate the bundles are truly protoxylem, 

 whether they are spiral or scalariform. 8 



m r 



Fig. 4 Fig. 5 



Figs. 4, 5.— Cycas media: fig. 4, transverse section of stem, showing only centripetal 

 end of bundle of innermost cylinder; m, pith; mr, pith ray; px, distinct protoxylem; 

 t, unthickened xylem elements; X400; fig. 5, transverse section of stem, showing 

 centripetal end of bundle of innermost cylinder highly magnified; m, pith; px, pro- 

 toxylem; a;', primary xylem; pits apparent in none of these cells; X850. 



As in Wordsell's account, spiral tracheids here can be fol- 

 lowed more easily in leaf traces off the normal cylinder than they 

 can in the cylinder itself. The reason for this is not that these 

 elements have been destroyed in the cylinder proper, but that 



8 Chamberlain, C. J., The adult cycad trunk. Bot. Gaz. 52:97. 1911. 



