119 ELEMENTS OF PLANT ANATOMY. 
of three distinct parts, as may be seen on a cross-section ; 
a central cylinder or pith ; a zone surrounding this, which may 
be considered a hollow cylinder, of which the bundles form the 
chief part ; and outside of this another hollow cylinder consist- 
ing of the primary rind. (Fig. 47.) 
All leaf-traces which consist of, a Le strand, and nearly 
Fia, 49. Fie. 50. 
Diagrammatic sketch of the tangentially oblique course of the Plan of the course of the 
bundles in the young stem of Jberis amara. The bundles bundles in stem of Juni- 
which form the surface of a cylinder appear here spread pernana. s  leaf-trace 
out in a plane. 0, J, 2, etc., places where the leaf-traces bundles. k& bundle of 
enter the stem. — (After Naegeli.) bud. — (After Geyler.) 
all those with divided strands, run downward through more than 
one internode and then anastomose laterally with those of older 
leaves. That is, they are so inserted between the bundles al- 
ready in the circle that they do not break its course, and in this 
lateral union of the bundles similar parts always come in contact 
with each other, the xylem of the new with the xylem of the 
old, andsoon. (See Fig. 48.) The union of the new bundles 
with the old occurs either at the nodes or very near them, and 
