52 



GYMXOSPERMS 



with strongly cutinized epidermis. ITie leaves are thick, and their 

 internal structure shows that they were leathery and well fitted to 

 withstand adverse conditions (lig. 43). On the upper side there are 

 some thick-walled hypodermal cells and a well-marked palisade. 

 Near the middle is a single row of mesarch bundles with a strong 

 bundle sheath connected with the upper part of the leaf by scleren- 

 chyma cells. Below the bundles is a wavy line of thick-walled cells, 



Fig. 46. — Cycadeoidea ingens: photograph of a model in the Field Museum of Nat- 

 ural History in Chicago. The model is almost entirely of glass and was made by Mr. 

 Sella, with the aid of criticism and advice by Wieland. 



beneath which is a thick layer, extending to the lower epidermis, of 

 thick-walled cells. In the figure, only a few of these are clearly 

 shown, and although the preservation is good, the lack of natural 

 coloring makes most of the cells very indistinct. In the upper part, 

 the photomicrograph was retouched. 



The root. — Scarcely anything is known about the root of this 

 group. A paper by Dr. Stopes describes rootlets in a section identi- 

 fied as Bennettites saxbyanus, but these rootlets were probably ad- 



