78 OPHIOGLOSSACEAE [CH. 



or eight cells in each row of the neck, which, except that it is quite straight, 

 resembles otherwise that of typical Ferns. It is especially like that of 

 Osm7mda. The neck-canal-cell elongates, and the nucleus divides, but 

 usually without cell-division (Campbell). There has been difficulty in 

 recognising the ventral-canal-cell, but its presence need not now be held in 

 doubt. 



The underground prothalli of Hebnmthostachys are very irregular in form 

 (Fig. 378, a—d), but in essentials they resemble those of BotrycJiiuin. The 

 lower portion is lobed and hairy, and constitutes the region of mycorhizic 

 nutrition. It extends upwards into a cylinder free from fungus and hairless, 

 on which the gametangia are borne. There is a tendency to dioecism, but 

 in any case antheridia precede the archegonia which are distal. The anthe- 

 ridia are large and resemble those of Botrychium {e), while the archegonia 

 have, like BotrycJiium, projecting necks (/^ g). 



The prothallus of Ophioglossum is irregularly cylindrical. In O. moluccamtm 

 it maybe 5-10 mm. in length (Campbell), but in O. viilgatum it may attain 

 a length of 6 cm., and it is occasionally branched. There is often an enlarged 

 base, and it is here that the mycorhizic fungus is present. The upward- 

 growing apex is more free from it, and it bears the sexual organs, which are 

 very numerous and intermixed (Fig. 379). The antheridia are sunken as 

 before, and very large. Campbell found 250 spermatocytes and upwards in 

 the section of one antheridium of O. pendu/tiin, giving several thousands of 

 spermatozoids for each antheridium, "perhaps more than in any other 

 Pteridophyte" {Eusp. Ferns, p. 23). In O. moluccamtm the number is much 

 smaller, and that in O. viilgatum appears to take a middle place. In this we 

 see clearly a parallel with the respective sporangia of the species, for those 

 of O. pendulum are far the largest in the genus. The archegonia of Ophio- 

 glossum are more deeply sunk than in the other genera. O. pendulum shows 

 this in a pronounced form, but the structure of the archegonium is essentially 

 the same as in the rest (Fig. 380). Campbell remarks that in its earlier 

 stages it bears a striking resemblance to that of the Marattiaceae, which 

 the mature archegonium more nearly resembles than it does that of Botry- 

 chium. Even when mature the neck projects little above the surface of the 

 prothallium {Eiisp. Ferns, p. 29). 



It thus appears that the prothallia and sexual organs of the Ophioglossa- 

 ceae may be seriated according to the details above given, along lines 

 parallel to those based on their form, their anatomy, and their sporangia, 

 Botrychium virginianum and Ophioglossum pendulum appearing as specially 

 divergent types. 



