COMPARATIVE ANATOMY OF THE CYCADACES. 121 
EXPLANATION OF PLATES 15 & 16. 
The following are the abbreviations used in the lettering of the figures :— 
æ = xylem; æ’ = secondary centrifugal xylem; 2’ = centripetal xylem; 2°“) = centripetal xylem 
recently formed by a cambium ; pz = protoxylem ; ph = phloem; ph® = secondary centrifugal phloem ; 
p^' = centripetal phloem ; zi, 7*, r° = first, second, and third vascular rings respectively ; is = inverted 
strand; s = concentric cortical strand ; ss = small ditto ; ce = central cylinder; ir = intrafascicular 
ring ; lt = leaf-traces. 
Bowenia spectabilis, Hook. 
Fig. 1. Transverse section of a sub-concentric bundle in the cotyledon. 
2. Transverse section of a portion of the central cylinder of the root in the primary node, showing 
extrafascicular strands. 
Macrozamia Denisonii, F. Muell. 
Fig. 3. Transverse section of a concentric cortical strand just outside the central cylinder of the primary 
node. 
Medullosa Leuckarti, Gópp. & Stenz. 
Fig. 4. Transverse section of a concentric strand just outside the central cylinder of the stem. 
(Diagrammatic.) 
Cycas Seemanni, Al. Br. 
Fig. 5. Transverse section of a portion of three extravascular rings in the primary nodal region of the 
root. (Diagrammatic.) 
6. Transverse section of a portion of three vascular rings in the primary nodal region of the stem. 
(Diagrammatic.) 
Encephalartos lanuginosus, Lehm. 
Figs 7, 8, & 9. Transverse sections of portions of two vascular rings in the male peduncle. x 8. 
Ceratozamia mexicana, Brongn. 
Fig. 10. Transverse section of a portion of the vascular cylinder of the axis of the male cone. x 8. 
Ceratozamia latifolia, Miq. 
Fig. 11. Transverse section of the vascular cylinder of the axis of the male cone. x 8. 
Ceratozamia mexicana, Brongn. 
Fic. 12. Transverse section of a concentric medullary bundle in the axis of the male cone, x 60. 
KE 
SECOND SERIES.-—BOTANY, VOL. VI. 
