1914] 



HILL— A NA TOM Y OF L YCOPODI UM 



79 



L. verticillatum 



The stele of the strobilus in this species is characterized by the 

 differentiation of very few protoxylem points, 2 or 3 groups being 

 usual (figs. 24, 25). It differs from the other species in not being 

 radial at the apex. The organization of the stele in the strobilus 

 seems to be generally of the parallel-banded type from the first, 

 with a phloem group between two xylem bands, as sometimes 

 occurs in L. varium, and this develops into the crescent-shaped 

 xylem mass with phloem in the middle, as has been described for 



Figs. 24, 25. — L. verticillatum: transverse sections in series, showing the pro- 

 toxylem groups and the developing parallel bands; px, protoxylem; />, phloem; 

 X500. 



the other species (figs. 9, 26). This crescent-shaped mass breaks 

 up into the parallel-banded type, and then later at a lower level 

 in the strobilus axis, the metaxylem begins to grow inward and 

 breaks up the phloem band, forming a distinctly radial arrange- 

 ment (fig. 27). The phloem in this species is very difficult to 



recognize, and often even in the mature stem the extent of the 



phloem is uncertain. 



type 



mature 

 th rath 



lem 



The phloem i 



very limited in amount, and is scattered somewhat irregularly 



