THE ADULT SPOROPHYTE 87 



single season. In O. vulgatum the development of the leaf is very slow, the leaf 

 remaining three years inclosed in the bud and emerging in the fourth season. So 

 far as I know, no study has been made of the development of the leaves in those 

 species of the temperate climates where more than one leaf is developed in the season, 

 and it remains to be seen whether the leaves which unfold in the same season are 

 of the same age or not. In the rapidly growing tropical species it is exceedingly 

 unlikely that more than a few months are necessary for the complete development 

 of the leaf, which unfolds as soon as it is mature, but no data are available on this 

 subject. 



While the spike in Euophioglossum is usually inserted at the base of the sterile 

 lamina it may be attached much further down. This is especially noticeable in the 

 small species O. bergianum, from South America (see Bower 9, page 435). In 0. 

 bergianum the leaves do not show a clear separation into lamina and petiole and the 

 spike is inserted close to the base of the linear leaf, so that it appears to be an en- 

 tirely distinct structure. 



In nearly all of the species oi Euophioglossum the later roots, like the primary 

 ones, are monarch, but in O. bergianum they are diarch. In most cases at least, 

 as Holle (Holle 1) showed, only one root is formed for each leaf. This seems to be 

 the case in 0. moluccanum, which was investigated with some care. 



Ophioglossum pendulum (plate 4, B) is the best-known representative of Ophio- 

 derma, the second section of the genus. This differs a good deal in its general char- 

 acters from the small terrestrial species of Euophioglossum. It is not uncommon 

 throughout the eastern tropics, where it grows as an epiphyte upon the trunks and 

 branches of various trees. The rough stems of certain tree ferns and some palm- 

 like species of Phoenix form a favorite habitat for this fern in certain regions and, 

 as we have pointed out in the study of the gametophyte, it is frequently found rooting 

 in the masses of humus between the old leaf bases of some epiphytic ferns like 

 Asplenium nidus. The stem, instead of being upright, is markedly dorsiventral, 

 but is short, with the leaves crowded together near the end and all growing upon 

 the dorsal side of the rhizome, as they do in Helminthostachys (fig. 63). The leaves 

 are very much elongated and the ribbon-like lamina merges very gradually into the 

 extremely stout petiole. These leaves in large specimens may reach a length of 

 1.5 meters, or even more, and the long, strap-shaped leaves hanging down from the 

 boughs of the trees present a very characteristic appearance. In larger specimens 

 it is not uncommon to find the lamina dividing dichotomously (see plate 4, B) and 

 it is said that sometimes this dichotomy may extend to the petiole, in which case 

 each segment of the leaf bears a separate spike. 



The venation of the leaf is reticulate, the veins inclosing long, narrow meshes 

 with no free veins, and the venation thus resembles the type represented in Euophio- 

 glossum by Ophioglossum lusitanicum. The larger plants always have several 

 leaves which are expanded at the same time and growth goes on uninterruptedly. 

 The leaves are crowded together and there is no evident internode between them, 

 but it is clearly seen that they are arranged in two rows on the flanks of the short 

 rhizome (fig. 63, A). The remains of the stipular sheaths surround the bases of 

 the leaves and these sometimes present the appearance of two small stipule-like 

 organs. As in Euophioglossum, adventitious buds are frequently formed upon the 

 roots. As a rule they are not terminal, but lateral structures and probably do not 

 differ essentially in their development from those of 0. moluccanum. 



The rhizome is more or less buried in the humus and the roots ramify through 

 this. Even in the very young plant the roots are branched and this branching 

 becomes very marked in the larger sporophyte. There seems to be some difference 



