48 Lang.—Prothalli of Ophioglossum pendulum 
(O . pendulum) , but in all the genera a tendency to the doubling 
of the outer wall by periclinal division exists. This occurs 
exceptionally in O. pendulum , normally and in all the cells in 
O. peduncidosum and Botrychium , while in Helmin thostachys 
several cells, through one of which dehiscence occurs, remain 
undivided. It may be assumed with probability that the one- 
layered wall represents the primitive condition, from which 
the other modifications have been derived. So far as is 
known (0. pedunculosum, Botrychium) the spermatozoids are 
multiciliate. The archegonia have a rather deeply sunken 
venter and a neck of four rows of cells which may hardly 
project from the surface ( Ophioglossum ), or be longer and 
project considerably ( Botrychium , Helminthos tacky s). A basal 
cell has been found in all in which its presence has been 
looked for. The most extensive central series seen consisted 
of the ovum, a ventral canal-cell, and a bi-nucleate neck-canal- 
cell (B. virginianum). 
The embryogeny is not completely known in all three genera, 
but the advanced stages of Ophioglossum and Helminthos tacky s 
show essential agreement with Botrychium , in which the seg- 
mentation is known in detail. No suspensor is formed. The 
whole of the hypobasal half forms the large hemispherical 
foot, while the first root, first leaf and stem-apex become 
distinguishable rather late in the epibasal half. The apex of 
the stem comes to occupy a depression in front of the first leaf. 
Having thus reviewed the common characters of external 
form, reproductive organs and embryogeny in the Ophio- 
glossaceae, the question arises whether a similar assemblage of 
characters is to be found in any of the three existing phyla 
of Vascular Cryptogams. There is little to suggest a close 
relationship between the Ophioglossaceae and the Equisetales, 
and the former group has usually been compared with the 
Lycopodiales or the Filicales 1 . In such comparisons it is 
1 Without summarizing the views expressed by these authors the discussions 
of the evidences of affinity afforded by the Ophioglossaceous prothallus by Bower 
(Studies II, Ophioglossaceae , London, 1896, p. 62), Jeffrey (loc. cit.) and Goebel 
(Organographie, p. 410) maybe referred to. 
