1913] PETRY—PROTOCORM OF OPHIOGLOSSUM 159 
and then divides into two strands which run almost horizontally 
and close the leaf gaps on either side. The leaf bundles correspond- 
ing to a gap sometimes attach to the vertical strands at the sides 
of the gap; much more usually, however, they connect with the 
horizontal strand above the gap, at about go° apart. 
In a single instance, three bundles separate from the strands of 
the cylinder. Two of these fuse at a very short distance from their 
points of connection with the cylinder strand, and the two resulting 
strands form the vascular supply of a leaf. 
Along a vertical strand the phloem is upon the inside of the 
cylinder and the xylem outside 
(fig. 6). Where the strands run 
horizontally the phloem is often 
upon the upper side. This twist 
of the strands never exceeds go”, 
that is, phloem never occurs on 
the outer side of a strand. The 
protoxylem is at the outer mar- 
gin of the xylem area (fig. 7). No 
endodermis can be distinguished 
about any of the cylinder 
strands; both xylem and phloem 
are bordered directly by un- 
modified parenchyma. Fic. s.—Model from above 
The leaf bundles, when they 
separate from the cylinder strands, run horizontally inward for a 
short distance, then run obliquely upward till they emerge within 
the central pit. At this point the two bundles of a leaf trace are 
about 0.5 mm. apart, and they run parallel to each other at this 
distance through that part of the petiole within the pit. 
In the petiole of thie leaf the xylem is adaxial, as in an ordinary 
plant. Where the leaf bundles are horizontal the phloem is above 
the xylem, and in this position the xylem and phloem connect 
directly with the corresponding tissues of the horizontal cylinder 
strands. In the few cases where a leaf strand connects with a 
vertical cylinder strand, the xylem connects directly. The phloem 
of the cylinder strand swings to one side to pass the xylem of the 
