12 Chrysler .— The Nature of the Fertile Spike in 
information on this point. The vascular supply of the fertile spike is 
derived partly from the odd bundle and partly from two strands which 
branch off from the right and left edges of the curved series of bundles 
which constitute the leaf-trace, but the odd bundle anastomoses with the 
main petiolar supply at the level of branching of the sterile segment, and 
emerges from this anastomosis as a pair of strands. Thus the vascular 
supply of the fertile spike consists of four strands. Upon this rather 
complicated system the young plant throws some light. Lang finds that 
the first leaves borne by the sporophyte contain only two bundles, derived 
by the splitting of a single leaf-trace. In this respect, therefore, the young 
plant resembles Botrychium. The small plant which came into my hands 
bore a fertile spike but possessed a simpler structure than the adult plant. 
The lower part of the petiole shows only four strands, two adaxial and 
two abaxial, i. e. the leaf-trace forks twice instead of three times as is 
the case in older plants. About half-way up the petiole, one of the adaxial 
strands gives off a rather small strand from the side which corresponds 
to one of the free edges of the curved leaf-trace (Fig. 22 ) ; the new strand 
takes a place midway between the two adaxial strands and runs up to the 
place where the fertile and sterile segments separate; here it anastomoses 
with the main strands (which in the meantime have united edge to edge) 
and finally emerges to supply the fertile spike. In this specimen there¬ 
fore the vascular supply of the spike is derived from one edge of the curved 
leaf-trace, and it will be recalled that in the mature plant part of the supply 
is so derived. We have already seen that in B. obliquum a single pinna 
may be fertile or may even turn upward and constitute a fertile spike, and 
it has been argued that some of the spikes of Ophioglossum palmatum may 
represent single pinnae or lobes, so that it appears probable that in the 
highly specialized Helminthostackys a single pinna functions as a fertile 
spike. 
The various theories regarding the fertile spike may now be considered 
in the light of the foregoing observations. The early suggestion of Roeper 
( 20 ) that two fused leaves are present in the aerial part of Botrychium is 
easily disproved by the well-known fact that a single bundle arises from the 
central cylinder of the stem, leaving a well-marked gap, hence the whole 
structure constitutes a single leaf. The same fact disposes of Braun’s 
surmise ( 7 ) that the fertile spike represents an axillary bud, for the vascular 
supply of the spike arises from the single leaf-trace, not from the central 
cylinder. 
The position of those who hold with Goebel that the fertile spike is 
a ventral lobe of a leaf is, as Bower remarks, somewhat obscure. If the 
organ is really ventral in origin, the vascular system ought to exhibit this 
feature, but it has been shown that in Botrychium , and probably in the 
other genera of the family, the origin of the vascular supply of the fertile 
