1914] PETRY—OPHIOGLOSSUM PENDULUM 187 
the leaf gap is actually closed (fig. 12, P; fig. 11, J); in some cases, 
however, all the strands connect within the lower portion of the 
opening in the cylinder. 
The general course of the strands in the leaf base is at a slight 
angle upward from the point of connection with the cylinder; in 
very large leaves, the lower ones may run horizontally or even in 
a downward direction. Branching of some of the strands usually 
occurs within the cortex of the stem, so that as many as 20 strands 
may be found in the base of the petiole. This may not occur in 
small sterile leaves, so that a section of the petiole may show as 
few as 3 strands. 
In the sterile leaves, the strands, 3-5 in number, arrange them- 
selves in the shape of a C, with the opening directed adaxially. 
The strands in the extremities of the arc in passing up through the 
petiole swing out toward the margins as the blade is formed, and 
all come to lie in a single plane with xylem adaxially directed. 
Frequent branching and anastomosing of the strands occur, so that 
€ number may reach 15 or 20 in the blade of the leaf. 
In the fertile leaves, the strands, 4-12 in number, are arranged 
in a circle or oval as they leave the cylinder, and they maintain 
this arrangement through the petiole. They branch and anastomose 
freely, forming a complete cylindrical network; no strands connect 
actoss the circle. As the petiole broadens and flattens, the strands 
arrange themselves in two series: the outer, consisting of 10-15 
strands with xylem directed adaxially, form the vascular system of 
the blade; the inner series, of 5-8 strands with xylem abaxially 
directed, is reduced by fusions to 4-6 strands which form the vas- 
cular supply of the spike. Anastomosing and branching occur 
48 before within each series, but there is no further connection 
between the two systems. Beyond the point of connection of the 
fertile spike, the single series of strands constituting the reticulate 
Veining of the blade may increase to as many as 30 in branching 
leaves. They form a closed system with the exception of a very 
few small branches which end blindly in the tip, 
In the leaf strands as they separate from the cylinder, the xylem 
elements are all alike, but in the base of the petiole and through- 
Out the leaf the first formed elements can be distinguished by their 
