64 



BOTANICAL GAZETTE 



[JULY 



from Samoa were com 



No 



young sporophytes were present in any of the 

 investigation of the anatomical structures of the pi 

 most interesting feature of study, and this 



ma 



An 



lirv 



was 



development 



material was studied from 



bearing upon phylogeny. The 



serial sections cut 10-15^ in thickness and stained in safranin- 



anilin blue and in safranin-light green. Since the material of 



com 



structures especially well, this 

 species was selected as a basis 

 for description and comparison. 



L. carinatum 



In the apex of the strobilus 

 of L. carinatum the outline of 

 the transverse section of the 

 young vascular cylinder is often 

 almost square. Within the first 

 millimeter of the stem, before 

 any lignification of the proto- 

 xylem is recognizable, there is 

 distinct differentiation of the 



tion of the stem near the apex, showing tissues; not Only IS the cyim- 



the organization of the young stele; e, der organized as a region dis- 

 tinct from the cortex, but the 

 elements of the tissues of the 

 vascular system are differenti- 

 ated. The large cells of the endodermis are discernible, inclosing 

 a mass of smaller cells. Dart of which have abundant cvtonlasm and 



Fig. 2. — L. carinatum: transverse sec- 



inner wall of endodermal 

 toxylem; large 

 nified potential 



X500. 



into 



conspicuous nuclei, 

 the vascular tissues. 



At this stage of development there are two distinct systems of 

 cells within the stele. The central region of the young cylinder is 

 occupied by 



;> 



asm 



forming 



unlignified 



These are to 



become lignified and form metaxylem. The angles of this radiating 



