GENERAL MORPHOLOGY 433 
maintained here, and is departed from in other species. The apex of the 
stock is occupied by a bud, and according to the season the outermost 
leaf (or sometimes two or more of them) may be extended above ground, 
or it may be still enveloped by the ochrea-like stipule of the preceding 
leaf (Fig. 236. 1, 2, 3). The bud on dissection shows that the apex 
of the axis is buried deep down among the successive leaves of the bud: 
each of these is provided with a large stipular sheath, which covers the 
bud, including all the succeeding spirally arranged leaves. There is no 
circinate venation. Each leaf develops slowly in the bud for three years, 
and expands in the fourth year. In spring the young leaf of the year, 
bursting the sheath of the preceding leaf, extends with an elongating 
petiole upwards, forcing its way through the soil: and the broadly ovate 
sterile lamina finally unfolds as a fleshy, undivided expansion, with 
reticulate venation. From its upper surface, at the point of junction 
with the lamina springs the fertile spike, a body which is stalked, and 
bears on either lateral margin of its upper part a dense row of sunken 
sporangia (Fig. 235 8, C, F,G): the tip of the spike is sterile. Terminal 
branching of the shoot is exceedingly rare: a case is recorded by Poirault. 
But that deficiency is made up by the frequent formation of adventitious 
buds: these may appear in relation to the axis (Fig. 236. 8), but more 
frequently upon the roots, where they arise in close proximity to the apex 
(Figs. 235 a, 236. 7). 
These external characters of the mature plant of O. wulgatum represent 
typically the salient features of the Adder’s Tongues; but to obtain a 
conception of the genus as a whole, it is necessary to examine other 
species, and they will here be taken in a sequence which is held to 
illustrate a morphological progression. The species are not all habitually 
monophyllous: several small species are found to be polyphyllous, showing 
constantly that condition which is exceptional in O. vulgatum (Fig. 235 B, J). 
Conspicuous among them is O. Bergianum: this rare little plant differs 
externally from other species in the fact that the fertile spike is inserted 
very low down upon the narrow linear sterile leaf, of which three or four 
are commonly expanded at once (Fig. 237). The number of sporangia on 
éach spike may also be very small; but notwithstanding these differences, 
the general disposition of the parts is that usual for the genus. The 
polyphyllous condition which it shows is shared also by O. dudbosum, Michx 
(=O crotalophoroides, Walt.), and especially by O. nudicaule, L. fil., where 
it appears to be common, and even habitual, four to six leaves being 
simultaneously expanded, and most of them bearing fertile spikes. In 
O. lusttanicum also, as well as in several other species, a plurality of leaves 
simultaneously expanded is the rule. That condition is most frequent in 
the smaller-leaved forms, and it may be held to connect the monophyllous 
habit as seen in the Ophioglossaceae with the polyphyllous strobiloid type 
common in other Pteridophytes. 
But the genus shows a capacity for amplification of the parts of the 
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