GNETALES— WELWITSCHIA 



391 



more numerous on the upper side, but there are many on the lower 

 side; Pearson^''^ counted 108 125 to the square miUimeter on the 

 upper side, and 87-96 on the lower. 



Fig. 368. — Welwitschia mirabilis: transverse section of flower stalk, next to the last 

 branch below the cones. Only one or two cells of each .\ylem row are pitted: the rest 

 have annular, spiral or reticulate marking; X370. 



In transverse section, the leaves show a single row of collateral 

 endarch bundles, each surrounded by transfusion tissue, and with 

 strands of thick-walled fibers between the transfusion tissue and the 

 xylem. There is a strong palisade both above and below, with bun- 

 dles of thick-walled fibers alternating with the palisade. Surrounding 

 the bundles is a thin-walled parenchyma, and, everywhere, except in 

 the bundles themselves, great numbers of spicular cells. A leaf could 

 hardly be better adapted to desert conditions. 



