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XIV. — The Anatomy and Affinity of certain Rare and Primitive Ferns. By 
John M'Lean Thompson, M.A., D.Sc., Lecturer in Botany, Glasgow Univer- 
sity. (With Seven Plates and Thirty Figures in the Text.) 
(MS. received February 4, 1918. Read February 4, 1918. Issued separately September 9, 1918.) 
A number of rare genera of Ferns of somewhat uncertain affinity had recently 
come to my hands. As 'they had by previous writers been referred in some degree 
to a common relationship it seemed well to embody them together in one memoir. 
As the work proceeded the justification of this became more apparent, and towards 
the end of the work the conclusion seemed clear that the suggested affinities were 
real though not very close. 
The genera in question were Jamesonia, Hk. Gr., Llavea, Lagasca, and Trismeria, 
F6e. Comparisons have also been made with Gymnogramme, Desv., Cryptogramme , 
R. Br., Cheilanthes, Sw., Notliochlaena, R. Br., Pellsea, Link., and Ceratopteris, 
Brong., while the facts already known for Plagiogyria, Kze., form a further basis 
for comparison, with a possible reference to a phyletic source in the direction of 
the Schizeeacese. 
Jamesonia , Hk. et Grev. 
In the leones Filicum of 1831 Hooker and Greville described a curious Fern 
discovered by Professor Wm. Jameson, Quito, at an altitude of 12,000 feet, on 
Mount Cayambe, Peru. The stem was creeping and much branched, the leaves 
slender and pinnate. The small coriaceous sub-flabellate pinnse bore a dense 
covering of tawny hairs. The pinna-margins were incurved as a .membranous flap, 
which was considered an indusium. The sporangia were scattered along the veins 
on the lower surface of the pinnse and were concealed by hairs. The sporangial 
stalk was short, the annulus almost vertical, and the spores tetrahedral. The distal 
portions of the veins were devoid of sporangia. The sporangial arrangement was 
considered remarkable and the hairs distinctive. Being then unable to refer this 
plant satisfactorily to any accepted genus, Hooker and Greville constituted a new 
one ( Jamesonia ) of it. 
In 1840 Kunze ( Farnkr .) followed the example thus set, and further claimed 
the existence of six species. In 1856 Mettenitjs attempted to divide the genus. 
He accepted as true species some of those already recognised, but referred the 
remainder to the comprehensive genus Polypodium , L., and to Gymnogramme, 
Desv. To Willdenow this plant was a Pteris, L. ; Desvaux named it Cheilanthes, 
Sw. ; and Presl reduced it to Allosorus, Berw. In 1864 Jamesonia appeared in 
the Species Filicum as the first genus of Hooker’s Grammatidse. It was thus 
TRANS. ROY. SOC. EDIN., VOL. LIT, PART II (NO. 14). 57 
