46 
Lang.—Studies in the Morphology and 
It would lead too far to extend the comparison in detail to the Cycado¬ 
filices and the Cycadaceae, but it must be pointed out that there is 
a close resemblance between the monarch stage of the leaf-trace in 
Helminthostachys and in Calamopitys , a resemblance extending to the stage 
of division of the trace in the cortex. This comparison may be also applied 
to Lyginodendron , and the reality of the adaxial completion of the xylem in 
Helminthostachys supports the interpretation of the ‘ mesarch ’ bundles of 
Lyginodendron as closed divergents. 1 This view does not necessarily 
prevent a comparison of the bundles of the latter plant with those of 
Cycads, for one way of regarding them would be as derived from such 
a closed divergent. 
These comparisons, without fully treating the subject, will indicate that 
the leaf-trace of Helminthostachys resembles those of the Osmundaceae, 
Zygopterideae, and Cycadofilices more than it does those of the more 
modern leptosporangiate Ferns. 
( d) The branching of Helminthostachys also affords suggestive points 
of comparison with the Zygopterideae and Cycadofilices. The branching is 
definitely axillary, and buds or branches in this position are known in some 
'vgopterideae and in Lygmodendron . Among other Ferns axillary 
jranching is only known in the Hymenophyllaceae. This position of the 
lateral branches is the characteristic one in the Cordaitales and in the 
modern Conifers and Angiosperms. 
The branching of Helminthostachys may first be compared with that of 
Botrychium . In both these genera of Ophioglossaceae there is a regular 
development of dormant lateral growing points or vestigial buds in an 
axillary position. From these, when the normal correlation is disturbed by 
the arrest of the growth of the main axis, lateral branches may develop. 
In Botrychium lunaria the vascular system of the branch is in relation with 
the adaxial side of the subtending leaf-trace. In Helminthostachys , on the 
other hand, while the relative position of the branch and the subtending 
leaf-trace is the same, the vascular connexion is with the stele of the 
rhizome some distance above the level of the leaf-trace departure. In the 
case of one branch at least it has been proved that the inner xylem of 
the branch stele was continuous with the inner xylem of the rhizome, while 
the outer xylem was continuous with an accessory or secondary develop¬ 
ment of the outer xylem of the main stele. Had the branch developed at 
once, instead of after the stele of the rhizome was mature, the inner and 
outer xylems would both doubtless have been continuous from the main 
stele to that of the branch. This primary relation is indicated in the 
structure of the vascular disturbance behind some vestigial buds. 
The vascular connexion of the axillary branch in Botrychium lunaria 
1 Chodat: Arch. d. Sc. Phys. et Nat., 1908. Cf. also P. Bertrand : Etudes sur la Fronde des 
Zygopt^ridees (Lille, 1909), pp. 264 ff. 
