628 Bray: THE Tissues OF SOME OF THE 
leaf is marked lengthwise by alternating bands of mechanical and 
assimilation tissue. The conducting tissue (/ 6, vs) is enclosed 
in the bands of mechanical bast-cells. In Vo/zza also the epider- 
mis (cz) has very thick, rigid walls and plays an important part 
as mechanical tissue. 
: S SS 
ZSSSSSc0 sl 
erst ee ee 
SE ek Spee oe 
« * . 
ha cete 
Fic. 7. Cross-section of epidermal region of Ariocarpus fissuratus, transversely 
through a stoma. ¢f, the double-layered epidermis with heavy binding wall, ¢/, and 
greatly developed cuticular (chitin-like) layer cz; sf, the stomatal pit leading down to 
the guard-cell apparatus, g, a, a, a, and interrupted by numerous diaphragm-like out- 
growths, /am, with apertures, af, so placed as to make a sort of spiral; sc, the suc 
cessive still-air spaces; 4, line of rupture between cellulose and cuticular layers of eplr 
dermis. 
4. Ariocarpus fissuratus (Anhalonium fissuratum) commonly 
called the star-cactus and living-rock cactus, has a fleshy turnip- 
shaped body growing almost hidden in the dry adobe and with 
the exposed part so dusty gray as to be difficult to distinguish 
a 
