344. Knox: STEM OF IBERVILLEA SONORAE 
Explanation of plate 24. 
The figures were drawn with Leitz lenses and an Abbé camera-lucida and the 
ee have here diane oni e casio in saitaaesessai 
/,, outer leptome ; /2, inner 
1. Diagram 
letome st, ‘venation h, hadrome; x, “bundle ‘pctaved | in FIGURE 10. 
F ransverse section of portion of cortex of primary stem. ¢, epidermis ; 
col, fh Aa ; ch, chlorenchyma ; 0s, obliterated sieve-tubes ; end, endodermis; s¢, 
tereome 775. 
s. 3 and 4. Transverse sections of portions of cortex of young stem. ¢, epi- 
dermis ; co/, collenchyma ; st, stereome ; ec. s, ectocyclic sieve-tube ; em. s, endocyclic 
sieve-tu 975. 
Fics. 5-8. ‘Transverse sections of cortex of stems, showing appearance of groups 
of obliterated sieve-tubes. s¢, stereome ; p7, parenchyma; //, phellem ; pa, phel- 
loderm. Fic. 5, saviobeey of outer ieee FIGs. 6-8, cortex. XX 650. 
Fic. 9. Diagram of transverse section of two-year stem. /, periderm ; 
ated sieve-tubes ; 4, hadrome; 4, outer leptome; /,, inner leptome; 5/, stereome. 
os, obliter- 
Fic. 10, Transverse section of bundle of inner ring showing inner een of a 
primary stem. Fic. 11 the same on a secondary stem. /. ¢, pitted duct ; 
duct; 2. 2, skp oppor ie inner cambium; s, sieve- tube ; Os, saienedda sieve- 
tube ; — ge eae * 480. 
. Transverse section of old secondary stem showing tertiary bundle. The 
arrow vel the ee of the axis of the primary bundle. Lettering as in FIGS. 
1o and 11. 
Fic. 13. Diagram of section of very old stem. Lettering as before ; 4g, tertiary 
bundle. "The shaded portions are leptome. > 180. 
