700 PROFESSOR W. C. WILLIAMSON AND DR. D. H. SCOTT ON THE 
en, Endodermis, which is evidently double. 
c, c, Cells of inner cortex. 
Lz. Part of lacunar zone. The dark cells may have beon secretory sacs. 
Fig. 5. Transverse section of a diarch rootlet. O.N. 1318. x 70. (See p. 692.) 
px, px, The two protoxylem-groups of the primary xylem-plate. 
About five layers of secondary wood have been formed. 
ph, Remains of phloém. 
The endodermis has divided tangentially ; lacunar zone (J.z.) and epidermoidal 
layer are shown. 
Fig. 6. Part of a tangential section of the wood of a root, showing the base of a 
lateral root. C.N. 1358. x 100. (See p. 695.) 
x, Secondary wood of main root. 
rv, Secondary rays. 
p, Pith of lateral root. 
x, Primary, «”, secondary xylem of lateral root. 
From the course of the trachez, we infer that the bottom of the figure is 
directed towards the organic base of the main root. Cf STRASBURGER, 
‘ Histologische Beitrage,’ III., p. 136. 
PLATE 17. 
Fig. 7. Transverse section of a rootlet, probably triarch, without secondary wood. 
C.N. 1890. x 50. (See p. 692.) 
lz. Lacunar zone of cortex. 
ep, Epidermoidal layer, which is especially clear. 
One side of the cortex is omitted, 
Fig. 8. Oblique section of a branching rootlet, probably tetrarch, with little or no 
secondary wood. C.N.1892c. xX 80. (See p. 692.) 
lz. Lacunar zone of cortex; the trabecule show the commencement of 
thyiosis. 
ep, Epidermoidal layer. 
br, Branch-rootlet, probably diarch, passing out through the cortex of the 
main rootlet. 
Fig. 9. Oblique section of a branching diarch rootlet, from the same preparation as 
fig. 8. The xylem-plate is not yet lignified in the middle. C.N. 18920, 
x 100. (See p. 692.) 
px, px, The two protoxylem-groups, to one of which the xylem of the 
branch-rootlet, br, is attached. 
en, Endodermis. 
The endogenous origin of the branch is evident. 
