370 BOTANICAL GAZETTE [NOVEMBER 
consecutive primordia. Evidences indicate that a scale is not pre- 
determined, but remains abortive through some variable cause. The 
primordia, whether developing scales or leaves, show the same struc- 
ture in every particular. 
The leaf traces.—The course of the leaf traces in the seedling are 
the same in general plan as those described for the embryo, but the 
girdling in the older leaves and scales is much more marked. The 
internal growth and the appearance of new organs has crowded the 
older parts farther and farther outward. ‘The circumference of the 
cortex has increased materially, and also the length of the vascular 
strands running through it. In the older scales and fully developed 
leaves these are all of about the same extent, and almost horizontal; 
but from these, through the younger leaves and scales to the youngest 
primordia, the sweep of the girdle diminishes; but the girdles are 
anes established in the very youngest of the primordia (figs. 34, 35) 
8-) : 
Although in the strands of the youngest leaf primordia no xylem 
elements are present, the courses of the bundles may be made out 
readily because of the arrangement, the staining qualities, and shape 
of the cells, which have denser protoplasm and larger nuclei, and are 
longer than the adjacent cells (figs. 26, 27). ‘The strands of the very 
youngest primordia which have their origin on the opposite side of 
the central cylinder show the girdling habit in the same manner - 
those of the older leaves, but on a smaller scale. The girdle does 
not always take the horizontal direction, but may be more oblique at 
the beginning (figs. 4, 5, 34, 35). Fig. 35 shows this clearly, in which 
pc is the procambium and lig the girdle of the youngest primordium. 
So long as such a strand is outside of the procambium it can be followed 
easily, but is lost after it has entered it. 
In the oldest plant examined (three or four years old); the firsts 
second, third, and fourth leaves displayed exactly the same — 
si was shown in the young leaves of the embryo and seedling. ag 
in the older leaves, outside of these, it is impossible to determine 
whether the described order is retained, because of the difficulty ™ 
following up strands of such size; but it is certain that anastomos 
are more frequent, due to the close proximity of crossing bundles. 
The transition of the xylem.—The strands of the older leave its 
