1915] PETRY—OPHIOGLOSSACEAE 351 
wing of xylem rounds up to form a single branch stele. This 
is exactly the behavior of each of the two wings in the first specimen. 
The vascular supply of the branch is here derived in part, at 
least, from adaxial extension of the centrifugal xylem of the leaf 
trace, as in B. Lunaria; but the formation of either one or two 
wings of xylem and the consequent formation of one or two branch 
steles is unique. The significance of this will be discussed later. 
®)W99 
Fic. 5.—Transverse sections of a branching rhizome of Botrychiwm virginianum; 
Botrychium virginianum.—Two branching rhizomes of this 
Species were examined; one of these bore two branches, the other 
a single one. Fig. 5 ou the vascular connections of the branch 
in one of these; nae injury occurred at the side of the stem and 
destroyed almost the entire stele (fig. 5,G,H). As indicated by 
the figure, there is a development of xylem in the space between 
the outgoing leaf trace and the stem stele, as in B. ramosum; but 
