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. i, 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 B, c, F, o) : 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 

 (%s. 235 A, 236. 7). 



These external characters of the mature plant of O. vitlgatum 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 

 each 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. ln<ll>ostini, Michx 

 ( = O crotalophoroides, Walt.), and especially by O. nudicaulc, 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. lusitanicum 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 



2 E 



