ANATOMY AND AFFINITY OF CERTAIN RARE AND PRIMITIVE FERNS. 379 
The anatomical characters of Llavea are such as to allow of a reasonable compari- 
son with Jamesonia, which the sporangial variations tend to strengthen. But at 
the same time a Plagiogyria, Kze., connection is suggested. This plant has been 
placed by certain systematists near to Llavea and Cryptogramme, and this connection 
is suggested by Christensen in his Index Filicum, 1905. Professor Bower has 
shown that Plagiogyria has hairs but no scales, a mixed sorus, an oblique annulus, 
and a solenostelic or slightly dictyostelic condition ( £< Studies in Phylogeny of 
Filicales,” No. 1 , Ann. Bot., 1910). This suggested connection with Plagiogyria 
is probably a reality. 
The spore-output of Llavea is on an advanced footing of reduction which forbids 
a view of close affinity between Llavea and J amesonia. It is hardly to be expected 
that development will be parallel on all lines. Accordingly the view that is taken 
is, that while in Jamesonia the annulus and stalk are in general advanced, the spore- 
output is primitive ; in Llavea the spore-output and stalk are advanced, and the 
annulus generally primitive, In Cryjptogramme, on the other hand, the sporangia 
are advanced on the condition seen in Llavea, but primitive characters persist in 
the stalk. 
The facts detailed justify the maintenance of Llavea as a monotypic “Acrostichoid” 
genus. As in the case of J amesonia, a suggestion of some Schizseaceous source for 
Llavea seems not unreasonable. The anatomical state will bear it, and, in light of 
the facts now available regarding Jamesonia, the sporangial state may support it. 
If this view be adopted, Llavea may be regarded as a more advanced derivative than 
Jamesonia, which has adopted a relatively small spore-output. 
Gymnogramme ( Trismeria ) trifoliata, Desv. 
There remains to be considered a remarkable Fern of tropical America which is 
considered by some systematists a species of Gymnogramme, and by others a distinct 
genus Trismeria, with one species and several sub-species. Its “ Acrostichoid ” 
character was recognised by Linnaeus in 1753, and he named it Acrostichum 
trifoliatum ( Sjp . PI.). It was similarly named by Swartz in 1806 (Syn. Fil.), by 
Schkuhr in 1809 (Fil.), and by Willdenow in 1810 (Sp. PI.). In 1811 Desvaux 
(Berl. Mag.) held it to be a Gymnogramme, and in 1827 he restated his belief in 
its Gymnogramme nature (Journ. de Bot. appl.). The opinion of Fee (Gen. Fil.), 
in 1850-52, was that this plant is neither an Acrostichum nor a Gymnogrammej 
but that it merits recognition as a distinct genus. He accordingly renamed it 
Trismeria. The opinion of Desvaux was upheld by Sir Wm. Hooker in 1862 
{Garden Ferns), and by Baker in 1878 (Jo. B.). In 1896 Kuhn designated it 
Ceropteris (Engl. Jahrb.), and in 1897 Christ named it Gymnogramme trifoliata 
(L.), Desv. (Farnkr.). Both Diels and Christensen have maintained it as a distinct 
genus Trismeria, the former in 1899, 1902 (Engler and Prantl, Nat. Pfm.), the latter 
in 1905 (Index Filicum). 
TRANS. ROY. SOC. EDIN., VOL. LII, PART II (NO. 14). 
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