XXXIl] 



PEOTOPITYS 



211 



form of the bordered pits on the radial walls of the tracheids 

 (fig. 462, D). The centre of the stem is occupied by a parenchy- 

 matous pith, elliptical in transverse section, enclosed by a band 



s*v. 







->-^^ 



era 



CD 



CDC 



OCX. 



CD 



^ 



p8o 



■O.O 



Pig. 462. Protopitys Buchiana. A, B. Central region of the stem showing 

 the pith, the primary xylem (black in fig. A) and (A) the inner part of the 

 secondary xylem; a, shoulders of xylem at the leaf -gaps; It leaf -trace; 

 px protoxylem. C. Secondary, x', and primary xylem, x^. D. Radial 

 longitudinal section of the secondary xylem. E. Soalariform tracheid of the 

 primary xylem. F. Pits on the meduUary-ray cells. (After Solms-Laubach.) 



of primary xylem composed of large polygonal tracheids (fig. 462, 

 C, x^) characterised by a dehcate scalariform pitting on all their 

 walls (fig. 462, E). The primary xylem forms a narrow layer on 

 the sides of the elHpse, 1 — 3 elements broad (fig. 462, A, B), but 



14—2 



