454 BOTANICAL GAZETTE [JUNE 
sinus at the inner edge of the xylem (stage 10). This sinus lies 
opposite that in the outer edge of the metaxylem, and the latter 
is broken in this region by the deepening of both notches; through 
the break inner and outer endodermes become confluent. Soon 
the endodermis becomes double in the region of involution, and 
two separate bundles are reconstituted, alternating with those of 
the internode below. The inner part of the endodermis of the 
departing trace arises as a duplication of that part of the invagi- 
nated endodermis that constitutes the bundle sheath of the new 
bundles at the sides of the parenchymatous depression in the 
outer edge of the nodal xylem. It is at this moment that the 
serauactin =? 29 
14” 
Fic. 4.—Stages 12-14: en.tr, endodermis of trace; other lettering as in preceding 
figures; X about 120. 
leaf trace finally becomes free from the axial tissues (fig. 3, 
stage 11). 
As we pass upward above the departure of the traces, the 
nodal xylem of the newly constituted bundles diminishes in amount, 
and these become more and more widely separated (fig. 4, stages 
12-14). Each of them carries with it two small groups of proto- 
xylem, situated laterally at the inner limit of the nodal xylem. 
Traced downward, these groups are continuous with the proto- 
xylem of two neighboring but independent bundles of the internode 
below. As the nodal xylem diminishes, the two groups of proto- 
xylem adherent to it are brought nearer to one another, each 
becoming farther and farther removed from its sister strand, now 
included in a neighboring bundle. Just before, or when the new 
bundles become free from one another, a slight depression appears 
in the outer edge of the xylem, in the median region of each new 
