lO Weiss, Root-apex ami Young Root of Lyginodcndroii. 



EXPLANATION OF PLATE. 



Fig. I. — A longitudinal section of root-apex of Lygiuodendron 

 from preparation in the Manchester Museum. Slide 

 R. 646. X 125. The section is slightly tangential. 

 Indications of the central cyhnder are visible, but the 

 actual initial or initials of the apex are not seen. 

 S.C. = secretory cells of inner cortex ; three of these are 

 nearer the root-apex. r.c. = root cap. This massive 

 root cap seems to be made up of a series of layers. 



Fig. 2. — Longitudinal section root-apex of young root-apex of 

 Lygitiodetidron from Slide R. 614. x 150. This 

 section shows the large size of the cells of the root 

 cap. The section is tangential, so that none of the 

 secretory cells of the niner cortex are seen. 



^^t,- 3- — A tranverse section of rootlet of Lyginodendrofi taken 

 very near the apex, as can be seen from the remains 

 of the root cap {r.c.) surrounding it. Slide R. 617 in 

 the Manchester Museum, x 244. The outermost 

 two layers are the characteristic exodermis. s.c. = 

 secretory cells of inner cortex. Note intercellular 

 spaces en. = endodermis consisting of six cells. 



Fig. 4. — Section across a young rootlet, showing distinctly the 

 exodermis, the thin walled inner cortex, with secretory 

 cells, the entodermis and the two groups of proto- 

 xylem of the diarch root. 



Fig. 5. — Longitudinal section through a rootlet of Lygiuodendron 

 at a point where a lateral rootlet is cut across. A 

 vertical row of tracheids of this diarch rootlet is seen 

 near the centre of the section Slide R. 1025-6 in 

 the Manchester Museum. xi2^. 



