the Oph ioglossaceae. 3 
The vascular supply of the aerial part of Botrychium virginianum 
arises as a single curved collateral strand (Text-fig. 1) from one side of the 
hollow cylinder of the underground stem, leaving a distinct gap. At 
a height of a centimetre or so the strand divides into two, and assumes 
a somewhat horseshoe shape, with its adaxial side concave. At about this 
level it gains an internal phloem and thus becomes concentric (Fig. 2) ; 
it retains this character as it rises through the stipe. At a distance of 
1-2 cm. below the point where the fertile and sterile segments separate, 
each arm of the horseshoe-shaped strand becomes hooked, and soon the 
tip of each hook breaks off as a small circular concentric strand (Fig. 3), 
Figs. 8-13. Diagrams illustrating the origin of the strands which supply the first pair of pinnae 
of the sterile segment in Botrychium virginianum. Fig. 8 follows Fig. 7 in the sequence. 
which a little higher up joins the inner face of the large strand (Fig. 5). 
Just at this level the adaxial portion of each arm of the main strand breaks 
off (Figs. 6, 7), and the two bundles so formed approximate to a certain 
extent and constitute the vascular supply of the fertile spike. Thus the 
fertile spike has a pair of bundles, as was pointed out long ago by Roeper. 
Before inquiring into the meaning of the peculiar course of the strands just 
traced, it will be well to follow up the main vascular supply into the sterile 
segment. The two main strands may unite at about this level or may 
remain slightly separated, and in any case they again begin precisely 
the same series of changes as has been described above, namely, the 
double strand assumes the form of a horseshoe with each point incurved 
