230 



BOTANICAL GAZETTE 



[SEPTEMBER 



The number of protoxylem points in the stem stele ranges 

 from 4 to 1 1 , with about 7 as the most frequent number. Sections 

 of the young stem tip show the condition characteristic of Lycopo- 

 dium, in which at about the time of differentiation of the proto- 

 xylem points the metaxylem cells are distinguishable by their 

 large size and lack of protoplasmic content (fig. 2). There are 3 

 so-called types of stele to be found in L. reflexum: the radial 

 arrangement (fig. 3), the parallel-banded arrangement (fig. 4), 



Fig. 5. — L. reflexum: stele showing inner cylinder of xylem surrounding strand 

 of phloem, most frequent arrangement found in stele of L. reflexum; X2cx>. 



and an arrangement consisting of an inner cyhnder of xylem sur- 

 rounding a strand of phloem (fig. 5). These 3 arrangements of 

 the xylem may be found in the same stem at different levels, and 

 are all modifications of the radial arrangement. The parallel- 

 banded arrangement, in which alternating strands of xylem and 

 phloem occur in parallel bands across the cylinder, seems to be 

 correlated to some extent with the growth of roots, since this 

 arrangement is to be found most frequently in the region where 

 the roots arise. The arrangement most frequently found is that 

 consisting of an inner cylinder of xylem inclosing a strand of 

 phloem (fig. 5). From this cylinder strands of xylem radiate to 



