364 BOTANICAL GAZETTE [NOVEMBER 
edge of the cotyledon on one side, and the other branch from the 
same protoxylem group into the corresponding edge of the other 
cotyledon. This may be stated in another way. In tracing down- 
ward, the four strands of each of the petioles of the cotyledons may 
be said to join two by two. Just before reaching the central cylinder 
the inner strands of each fuse, and the outer strands of the one fuse 
with the outer strands of the other, the four strands thus formed 
giving rise to the four protoxylem groups. This is shown semi- 
diagrammatically in figs. 4-6. Tracing these strands farther upward, 
they are found to branch once more, so that in the upper part of each 
cotyledon there may be as many as eight strands; but before reaching 
the tips of the cotyledons they reunite into one concentric bundle 
(fig. 15), which abuts immediately against the epidermis, thus com- 
ing into very close contact with the gametophyte. At this place the 
tissue of the gametophyte is so closely attached to that of the cotyledons 
that it is difficult to separate them. 
The vascular strands of the leaf primordia.—For each leaf or leaf 
primordium four strands leave the vascular cylinder or vascular plate, 
at points not definitely located, but quite well distributed, and 
generally in such a way that approximately one strand for each leat 
or primordium leaves on each side of the squarish central vascular 
cylinder; also those strands belonging to the first leaves have their 
origin either in the neighborhood of or in the protoxylem groups of 
the plate. Two strands leave the cylinder approximately oD ~ 
Same side as that on which the leaf for which they are destined 1s 
located, and run more or less directly through the cortex into the ven" 
tral part of the petiole without further branching; while the oth “ 
two strands leave the central cylinder approximately on the opposite 
_ Side and describe a curve around it (the one in one direction and the 
other in the opposite direction) through the cortex, through the sheath- 
ing leaf base, and finally into the dorsal or adaxial part of the petiole, 
where they branch and rebranch ( figs. 4-6). It should be empha 
sized that the point of origin is not at all definite, and that any pau 
lar girdle does not describe an arc of any definite extent, but i = 
length of the arc depends upon the place of origin of the girdle " 
the position of the leaf to which it belongs. aoe 
It has been said that that edge of the leaf base toward which t 
