COMPARATIVE ANATOMY 333 
2 
number from three to eight, as slightly projecting groups of small spiral 
tracheides. The condition thus attained is very similar to that seen in 
the simpler types of Lycopodium: or a better comparison may perhaps 
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Fic. 174. 
Lepidodendron Harcourtit, A=transverse section of stem; sf=stele; o.c =outer 
cortex ; both here and in the outer cortex the leaf-traces are shown about natural size. 
£B=stele of same ; f=pith, hollow in the middle ; +=xylem-ring ; Ax=protoxylem-points. 
The leaf-traces join the stele between them; ¢2.¢=leaf-trace bundles, of which the outer, 
2.t', show xylem and phloem; z.c=inner cortex. x7. (From Scott's Studies in Fossil 
Botany.) 
be drawn with certain stems of Zepidodendron. The presence of central 
and peripheral protoxylem in different parts of the same shoot should be 
a warning against too great reliance upon such characters ; it may, perhaps, 
indicate that the central position was the more primitive, as is believed 
by some on general comparative grounds. At the same time it is of 
