no 



THE OPHIOGLOSSALES 



Sterile lamina. In the larger species, like B. virgtntanum, many hundred sporangia 

 may be developed upon a single sporangiophore. In these larger and more special- 

 ized forms the sporangium is usually smaller and is better differentiated, always 

 having a more or less distinct pedicel. 



The form of the sporangiophore in Helminthostach \s is to some extent inter- 

 mediate between that of Ophioglossum and Botrychium, but on the whole comes 

 nearer to Botrychium. The sporangia are densely crowded along the flanks of the 

 spike, thus forming two rows somewhat as in Ophioglossum, but they are very much 

 more crowded and are formed in groups or synangia which project free above the 

 surface of the young spike. The sporangia do not arise singly, but are borne upon 

 short branches or secondary sporangiophores which suggest the lateral branches of 

 the sporangiophore in Botrychium, but are far less regularly disposed. By the fur- 

 ther growth of the sporangia the axis of the spike is entirely concealed and a casual 

 examination would indicate that the sporangia were formed equally at all points of 

 its surface, but a study of the development shows that they are lateral in structure, 

 as they are in Ophioglossum. 



THE DEVELOP.MENT OF THE SPOR.-\NGIOPHORE . 



The sporangiophore in both Ophioglossum and Botrychium becomes visible at 

 a very early period. In Ophioglossum moluccanum I have found that the spor- 

 angiophore can be recognized even earlier than Bower has stated for O. vulgatum 

 and O. reticulatum. A median section of a very young fertile leaf in O. moluccanum 

 is shown in fig. 56, D. The apex of the leaf has scarcely become free and the apex, 



as well as nearly the whole of the 

 adaxial surface, is made up of 

 large columnar meristem cells, of 

 which it is difficult to say that 

 any one is the single apical cell 

 of the leaf. The leaf trace is al- 

 ready evident, passing into the 

 base of the young leaf, which is 

 strongly inclined foi-ward so that 

 the real apex of the leaf is not 

 directed vertically upward, but is 

 on the adaxial side of the leaf 

 rudiment. The apex of the young 

 sporangiophore arises from the 

 tissue immediately below the apex 

 of the sterile segment, and the 

 whole of the adaxial portion of 

 the leaf below the apex of the 

 young sporangiophore may be said 

 to belong to the latter and not 

 to the sterile portion of the leaf. 

 There is thus practically a dichot- 

 omy of the apex of the young 



Fig. 81. 



A. Longitudinal section of young sporophyll of Ophioglossum moluccanum, 



still inclosed in the stipular sheath, sh X50. 



B. Apex of sterile lamina, spj sporangiophore. 



C. Apex of sporangiophore. X125. 



D. Transverse section of a very young sporophyll, showing dichotomy of 



apex. X125. 



sporophyll, and the two branches (viz, the sterile segment and the sporangiophore) 

 are structures of equal rank. It would thus appear that the old view put forward 

 by Mettenius of two equal branches of the fertile leaf is probably the correct one. 

 It is probable that younger stages than those figured by Bower for 0. vulgatum and 

 0. reticulatum would show the same condition of affairs that we pointed out in 



