390 
DE JOHN M‘LEAN THOMPSON ON THE 
A General Survey. 
The characters of external form, dermal appendages, and anatomy detailed above 
do not appear decisive, though they would allow of affinities of these Ferns in a 
moderately advanced position with references distinctly downwards. 
It may be held that Jamesonia shows the most primitive vegetative state, with 
hairs but no scales, a simple solenostele, a simply-pinnate leaf, undivided leaf-trace, 
marginal pinna-trace supply, and an open venation. A slightly more advanced state 
is shown by Llavea. It has both hairs and scales, a wide solenostele, dimorphic 
pinnules like those of Cryptogramme, a large leaf-trace with an incipient perforation 
at its base, a marginal pinna-trace supply, and occasional reticulations in the sterile 
pinnules. Anatomically, Trismeria is decidedly the most advanced. Its dominant 
dermal appendages are massive scales, and the specialised wax-secreting hairs are 
restricted to the fertile pinnules. The stele is an advanced solenostele, the large 
pinnate leaf has a divided leaf-trace, and the pinna-trace supplies are of extra- 
marginal origin. 
In all three the sporangial arrangement is “ Acrostichoid,” the sporangia are 
initiated superficially in a “simple” state, but by interpolation a “mixed” condi- 
tion is subsequently established. The transition from the “ simple ” to the “ mixed ” 
sorus is sudden, there being no indication of an intermediate “gradate” condition. 
A state similar to that already demonstrated by Professor Bower for Plagiogyria 
and Cryptogramme (with which Llavea has been grouped) is thus recognised in 
the Ferns under discussion (Ann. Bot., 1910). 
When attention is turned from this uniformity of soral condition to the details 
of sporangial construction it is seen that the sporangial states of Jamesonia, -Llavea, 
and Trismeria run more or less parallel to the anatomical conditions already 
compared. Jamesonia is the most primitive, Trismeria the most advanced. In 
all three the sporangial-stalk is slender and threer rowed, the annulus is of variable 
position and construction, and the spores are tetrahedral. In Jamesonia the capsule 
is lopsided, the annulus is frequently irregular and oblique, the stomial construc- 
tion is variable, and the spore-count is exceptional in being beyond 64, a very rare 
occurrence in Ferns other than those recognised as definitely primitive. In Llavea, 
as in Cryptogramme and Plagiogyria, the capsule is lopsided, the annulus is irregular 
in form and position, the details of stomial construction are variable, but the spore- 
counts are lower than in Jamesonia. The number for Plagiogyria is 48, for Llavea 
and Cryptogramme it varies below 52. In these Ferns variability of form ‘and 
position of the annulus and stomium is common, but in Trismeria the annulus is 
typically vertical and regular, and only occasionally irregular. The stomium is of 
very constant form and construction, and the spore-count varies below 52. The 
recognition of Trismeria as a relatively primitive Gymnogramme, in which irregu- 
larities of the annulus persist, suggests the possible existence of sporangial irregularities 
