1908] DORET Y—CERATOZAMIA 213 
Other changes occur as the meriphyte ascends the petiole (c, ne 
Just below the first pair of pinnae the branching is rapid, and _— 
level where the blade is seen exteriorly to separate from » — 
there are four strands provided for it (7). In the rachis —— 
approximation takes place (2), and the number of bundles is — : 
two (m). Each enters a pinna and branches continuously (n, ie 
The growing point terminating the rachis has no vascular ae 
in this leaf, in this respect agreeing with the young leaf represente = 
fig. toa. As the plant increases in age, the meristem of this 63 
"tains its activity longer, producing a greater number of pinnae, as 
the seed plants. | i 
bos a in all the leaf traces is endarch in the central cylinder 
(fg. 26), but it soon 
becomes mesarch, with 
the protoxylem moy- 
ing outward by almost 
imperceptible degrees. 
t never reaches the 
exarch condition, how- 
ever; even in the tips 
of the pinnae there are 
always two or three 
elements of centrifugal 
Wood. Here and there 
May be seen a few 
elements of transfusion tissue. 
Mucilage canals are numerous in the leaf bases (jigs. oe 
but they have no more definite arrangement ee " ules 
base of the cotyledon. Throughout the regi ox a ca ae 
there is a gradual decrease in number, luscine ee rae 
due to fusing. Toward the upper levels of this region sisal ee 
times “rranged in two series, an adaxial row and an a About rem 
With a definite relation to the bundles (ext jig. 20). al (d) 
above the base, there is left only one in ( at an 
Which sists for half the length of the petiole (¢). 
The haces of the leaves as ct as of the cotyledons are persed 
thick layer of cork. As was seen externally, the hypocotyl is extre 
Fic. 2.—Cross-section of flattened cells from inner 
face of petiole near the base. 
