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1909] SINNOTT—MESARCH STRUCTURE IN LYCOPODIUM 145 
8. Scorr, D. H., The anatomical characters presented by the peduncle of 
Cycadaceae. Rieale of Botany 11:399-419. pls. 20, 21. VE 
9. Jerrrey, E. G., On the structure of the leaf in Cretaceous pines. Annals of 
Botany 22:207-220. pls. 13, 14. 1908. 
10. Eames, A. J., On leaf structure in Equisetum. Annals of Botany, ined. 
EXPLANATION OF PLATE X 
Fic. 1.—Lycopodium inundatum var. Bigelovii; longitudinal radial section 
through a leaf-trace. 500. 
1G. 2.—Lycopodium inundatum var. Bigelovii; transverse section of a leaf- 
trace near the margin of a mucilage cavity. 500 
Fic. 3.—Lyco podium lucidulum; transverse section of a leaf-trace. 500. 
1G. 4.—Lycopodium clavatum, longitudinal radial section through the margin 
of thé central cylinder, showing the single centrifugal metaxylem element on the 
right. 500. 
Fic. 5.—Lycopodium clavatum; transverse section through the margin of the 
central cylinder at the point of departure of a leaf-trace; the dark line of crushed 
cells marks the position of the protoxylem. 500 
Fic. 6.—Lycopodium obscurum; longitudinal ceded section through the margin 
of the central cylinder, showing centrifugal metaxylem as in fig. 4. X500 
Fic. 7. —Lycopodium clavatum; longitudinal radial section ahconiake a leaf- 
trace. soo. 
Fic. 8.—Lycopodium clavatum; transverse section of a leaf-trace. 500. 
Fic. 9.—Lycopodium tristachyum; transverse section of a leaf-trace. X500. 
