Fig. 78. — Dioon spimilosum: longitudinal section of mature wood, showing a leaf 

 gap with a leaf trace connected with the base of the gap by tracheids; above the leaf 

 trace is a mucilage canal; there are many small medullary rays, mostly one cell wide. 

 The dark spots are calcium oxalate crystals, m, mucilage duct; p and x, phloem and 

 xylem of leaf trace; s, scalariform tracheid. — .\fter Dr. La Dema M. Langdon.^''^ 



