SUMMARY 491 
The roots appear early: the first root (sometimes precocious and 
inordinately developed in accordance with the mycorhizic habit) is 
essentially lateral upon the slowly developing axis, and the indefiniteness 
of its position, above or below the basal wall, indicates its accessory 
character. The whole shoot is, in fact, a rooted strobilus, which remains 
usually simple; but its strobiloid character is disguised by the abbreviation 
of the axis, and by the slow succession and relatively large size of its 
leaves. 
The first leaf of an adventitious bud of O. vulgatum, or the third leaf 
in the sexually produced plant, may be fertile: in Botrychium Lunaria 
the ninth leaf has been seen to be fertile. Such data, limited as they 
are, show a record of early appearance of spore-producing members 
unequalled elsewhere. They indicate a high probability that all the 
leaves are of the nature of sporophylls, while abortion of the spike, so 
frequently seen in various degrees in later leaves, would account for ‘its 
absence in those first formed. These may be expanded above ground 
(Helminthostachys, O. pedunculosum, B. virginianum), or may be arrested, . 
and appear as mere scale-leaves. The latter is clearly,a consequence of 
the underground and saprophytic habit of the prothallus, which diminishes 
the necessity of early self-nutrition of the sporophyte, and thus leads to 
reduction of the first leaves of the shoot as a purely secondary condition. 
On the other hand, the underground habit leads, as already explained, 
towards a monophyllous development, with enlargement of the individual 
leaf. This is imperfectly realised in the smaller species of Op/zoglossum, 
which on our hypothesis would be the more primitive; but it appears 
typically, though not universally, in the larger-leaved forms. Comparison 
combined with biological reasoning indicates, then, that leaf-enlargement 
has taken place. The anatomical facts accord with this: the solid or 
slightly medullated xylem of the stock widens out upwards into a funnel 
or cylinder, with foliar lacunae, where the single leaf trace-strands pass 
out: the dilating of the stele follows the increase in size of the leaves in 
the individual: this may be held to prefigure that of the race. Probably 
the original foliar supply was here, as in the strobiloid forms, a single 
strand, and this is still represented by the single bundle of the leaf- 
trace. In O. Bergianum the single strand may be seen continued without 
branching some distance upwards into the leaf. The branchings which 
appear in other species early in its course may on our theory have 
followed upon the enlargement and elaboration of the leaf. The Ophio- 
glossaceae are phyllosiphonic from the first: but the case of Zimesipteris 
has been adduced as showing that a transition may occur from the 
cladosiphonic to the phyllosiphonic type: this may occur in any case 
where the balance between the axis and the appendage is disturbed, so 
as to increase the preponderance of the leaf. On our hypothesis of a 
strobiloid origin for the Ophioglossaceae this has been the result of the 
stunted development of the axis consequent on the subterranean habit, 
