SPERAIATOPHYTA 79 



rather extensively from this time on ; they were apparently 

 abundant in North America, both on the coastal plain and in 

 the formations of the continental interior. 



Fig. 28. — Transverse section of the New Jersey Upper Cretaceous palm, Palmoxylon 

 anchorus Stevens. This is an example of the often marvelous perfection of pres- 

 ervation of cell structure in fossilized plants. Portion of a large root ( X 130) ; 

 p., phloem, thin-walled cells, through which most of the organic substances 

 manufactured by the leaves pass down to the roots; .v., xylem, thick-walled 

 woody cells through which the crude materials absorbed from the soil pass up to 

 the stem and leaves; /., an internal vessel surrounded by sclerenchyma fibers, — 

 very thick-walled, strengthening cells, (.\fter .Stevens.) 



Class 2, Dicotyledones 



The dicotyledons usually possess the following characters, — 

 the plants begin with two seedling leaves, the cotyledons 

 (whence the name di-cotyledons) ; the leaves are usually netted- 

 veined. The stem is usually thicker below than above, with 

 the vascular bundles arranged to form a cylinder inclosing a 

 pith center ; as growth proceeds new cylinders are formed, and 



