380 
DR JOHN M‘LEAN THOMPSON ON THE 
The plant is well figured in Hooker’s Garden Ferns and in several of the 
systematic works. It is a tall, erect Fern of striking appearance, with almost erect 
axis bearing lax scattered brown, scales, and stout leaf-stalks arranged almost 
alternately. The leaves are pinnate, and the pinnae are numerous. The lower pinnae 
are petiolate, and for the most part ternate. Higher up the pinnules are usually 
in pairs, and in the upper part the pinnae are usually undivided. The pinnules are 
linear -lanceolate and of a sub-coriaceous nature. The sterile pinnules are entirely 
naked, but on the lower surface of the fertile pinnules are glandular hairs and a 
covering of a characteristic white or yellow wax, similar to that present in Cheilanthes 
argentea (Gmel.), Kze., and in the Ceropteris section of Gymnogramme. 
It is a common Fern from Cuba southward to Peru and Brazil. It is well 
represented in Jamaica and in the West Indian Islands generally. Professor Bower 
has found it in streams in Jamaica, with its roots well fixed in the shingle. 
The near affinities of this “ Acrostichoid ” Fern are clearly in doubt, for the 
opinions held by the systematists have not hitherto been tested against the facts 
of construction and reproduction. With a view to a full investigation being made 
Professor Bower, F.R.S., and Mr J. M. F. Drummond, B.A., F.L.S., collected abundant 
material in Jamaica, and it is to them that I am indebted for the plants from which 
the following statement has been constructed. 
Dermal Appendages. — The axis-scales are of an advanced lanceolate type, with 
broad base, slightly serrate margins, and accuminate tip (fig. 40). They are the only 
dermal appendages which have been found on the stem. The mature petiole and 
sterile pinnules are entirely naked, but the fertile pinnules bear on their lower 
surface numerous glandular hairs (fig. 4l). Structurally the latter resemble the 
capitate hairs characteristic of the “ golden” and “ silver” species of Gymnogramme , 
Nothochlsena, and Cheilanthes. As has been shown by De Bary ( Comparative 
Anatomy of the Phanerogams and Ferns), 1884, these capitate hairs secrete a 
resinous substance soluble in alcohol. To this secretion the “golden” and “silver” 
Ferns owe their dusty appearance. In our materials preserved in alcohol the hairs 
and general epidermis show no sign of a secreted substance, but in our herbarium 
specimens a yellow-green deposit of fine rods and granules covers the hairs and the 
entire epidermis, excepting the raised guard cells (fig. 42). The presence of this 
secretion is a general guide to the fertility of a pinnule, its absence is an index 
of sterility. In the Synopsis Filicum, 1874, Sir Wm. Hooker placed special reliance 
in his specific treatment of Gymnogramme on the glandular hairs and associated 
resinous secretions. He considered them indicative of kinship for species possess- 
ing them, and included in a section Ceropteris all Gymnogrammes — including 
G. ( Trismeria ) trifoliata — possessing these features. It will be shown in the 
following pages that on the summation of characters this plant may still be con- 
sidered a Gymnogramme. From this it follows that the basis of Hooker’s grouping 
of the section Ceropteris is justifiable. 
