N. E. Stevens — New Jersey Palmoxylon. 133 



from fifteen to twenty-five cells wide, so that in the large roots 

 the sclerenchyraa region with the vascular portions it contains 

 occupies only about half the stele. 



The central portion of the stele contains a variable number 

 of "internal" vessels, frequently from four to six, which do 

 not appear to be referable to any particular xylem group. 

 Compare (Drabble, p. 411). Each of these internal vessels is 

 surrounded by a region of dense sclerenchyraa from six to ten 

 cells in width. See fig. 20. The remainder of the central 



Fig. 20. 



Fig. 20. Portions of stele of large root with endodermis, showing peri- 

 cycle, alternate phloem (P) and protoxylem (X) groups in a zone of dense 

 sclerenchyma. The inner region of the stele shows lignified parenchyma 

 with large intercellular spaces, and an internal vessel (I) surrounded by a 

 zone of sclerenchyma. x 175. 



region of the stele is occupied by lignified cells with large 

 lumen and comparatively thin walls. These cells apparently 

 became torn apart as the root increased in size so that, in fully 

 developed roots, this central region has large intercellular 

 spaces. 



The stele of the smaller roots shows the same structure as 

 that of the larger ones, but the number of protoxylem groups 

 is much smaller. The root shown in fig. 21 had thirteen pro- 



