On the Prothalli of Ophioglossum pendulum 
and Helminthostachys zeylanica. 
BY 
WILLIAM H. LANG, M.B., D.Sc., 
Lecturer in Botany at Queen Margaret College , Glasgow University . 
With Plates I, II, and III. 
Introduction. 
T HE difference of opinion which exists among investi- 
gators who have studied the Ophioglossaceae, as to the 
phylogeny of this small group of Vascular Cryptogams, is 
well known. Palaeobotany has not afforded decisive in- 
dications of connecting links with either the Filicineous or the 
Lycopodineous phylum and comparative study of the existing 
forms is alone available in the solution of the problem. Thus 
the more extended and detailed our knowledge of all the 
stages of the life-history of the Ophioglossaceae becomes, the 
better will be the chance of discovering their relationship to 
other groups. In the present paper only the evidence afforded 
by the gametophyte is considered. The prothallus is already 
known in Ophioglossum pedunculosum 1 and in Botrychium 
Lunaria 2 and B. virginianum 3 . Since the characters of these 
prothalli are described in the text-books, and will have to be 
considered in the general discussion below, no summary of 
1 Mettenius, Filices Horti Rotanici Lipsiensis. Leipzig, 1856, p. 119, PI. XXX. 
2 Hofmeister, Higher Cryptogamia. London, 1862, p. 307, Pl. XLI. 
3 Campbell, Mosses and Ferns. London, 1895, p. 225. Jeffrey, The Gameto- 
phyte of Botrychium virginianum. Trans. Canadian Institute, 1896-7, p. 265. 
[Annals of Botany, Vol. XVI. No. LXI. March, 1902.] 
