192 BOTANICAL GAZETTE [MARCH 
well developed at this stage (fig. 3 G, H). The leaf trace passes 
out to the petiole undivided, and the stipules, which are not 
conspicuous at this stage, have no vascular strands. 
FOURTH AND FIFTH LEAF STAGES 
In the fourth leaf stage the commissural strand is well developed 
and separates from the leaf trace after the latter has passed a 
considerable distance from the central strand, then it approaches 
the opposite edge of the latter. This behavior is the same as shown 
in fig. 4 A-C. Meanwhile this edge of the central strand is 
approaching the commissural strand by the addition of vascular 
tissues, and when the two meet, fusion takes place (fig. 4 C-F). 
At this stage a mucilage canal appears in the center of the central 
parenchyma. ‘This divides where the leaf trace goes outward, and 
one branch follows the inner side of the trace. The fifth stage is 
very much like the fourth except that the strands are larger and the 
commissural strand leaves the leaf trace closer to where the latter 
comes off the central strand. The central strand has increased in 
size so that the root stele reaches only half way around the other 
side. No well defined endodermis is discernible in this and the 
subsequent stages. 
SIXTH AND SEVENTH LEAF STAGES 
The sixth and seventh leaf stages differ from the fifth mainly 
in the stipular region, which will be discussed later. 
EIGHTH AND NINTH LEAF STAGES 
In the eighth leaf stage a new feature presents itself in the 
appearance of a medullary strand. This strand is first visible 
coming off the inner side of the central strand opposite the junction 
of the ninth root (fig. 4). The medullary strand takes a diago- 
nally upward course, crosses the central parenchyma, and fuses only 
partially with the commissural strand immediately before the latter 
has met the central strand. Both join the edge of the central 
strand just below the junction of the tenth root (fig. 5 A-F). The 
commissural strand becomes an integral part of the central strand, 
but the medullary strand remains visible, joined to the inner side 
of the central strand, and passes upward to the upper level of the 
