372 
DR JOHN M'LEAN THOMPSON ON THE 
elongated stalk and vertical annulus are considered features of advance, but the 
frequent irregularities of the annulus are regarded as accompaniments of a change in 
the position of the annulus, with, perhaps, a downward spread of induration. In any 
case the sporangia are held to be of an upgrade type, in which variations of the 
annulus might naturally be expected to persist. 
But the most decisive point which has emerged from the study of this plant is 
the high spore-count. It gains its value from the rarity of occurrence of numbers in 
advance of 64 in forms other than those recognised as primitive. It is undoubtedly 
a primitive feature which in a phyletic treatment enhances the value of simple 
anatomical characters. In the case under discussion it strengthens the opinion that 
the dermal appendages, the leaf-trace characters, the “ simple ” sporangial initiation, 
and the irregularities of annulus are evidences of a primitive source, and that the 
stelar state, the “ mixed ” condition of the mature sporangia, and the regular vertical 
annulus are features of moderate advance. 
The characters described are sufficiently distinctive to fully justify the mainten- 
ance of the genus Jamesonia, and, in the absence of evidence suggestive of some 
other ultimate origin, they may indicate for it some Schizseaceous source. This 
question of ultimate origin will be discussed at length in the conclusion to the 
memoir. 
'Llavea, Lagasca. 
This second plant appears in the Synopsis Filicum, 1874, as Llavea cordifolia, 
Lagasca, the single representative of a genus allied to Cryptogramme and Pellaea. 
In 1816 the genus was founded by Lagasca for the reception of a plant dedicated 
to M. de la Llave (Gen. et Sp.). In 1827 Desvaux described it as Allantodia 
(Journ. de Bot. app.), and Sprengel considered it an Asplenium ( Syst . 4). 
In 1839 Kttnze sank it in the comprehensive genus Allosorus (Filices), and it 
was similarly treated by Keyserling in 1873 (Pol. Cyath. Hb.). In 1831 Sir Wm. 
Hooker named it Ceratodactylis (leones Plantarum) ; and in 1839, 1842, J. Smith 
maintained this name (Hk. Gen. Fil.), remarking that “ the sterile portion of the 
frond agrees with Osmunda, and the fertile pinnules with Ceratopteris, and the 
position of the sporangia and form of the sorus with Cryptogramma.” He accord- 
ingly named the species Ceratodactylis osmundoides, but found it difficult to 
suggest what is its nearest affinity. It is the Botryogramme of Fee (Genera), 
1850-52, and a Cryptogramme according to Prantl, 1882. In 1897 Christ fol- 
lowed Hooker in maintaining Lagasca’s foundation (Farnkr.), and likewise associated 
it with Cryptogramme and Pellsea. In this he has been supported by Diels (Engler 
and Prantl, Nat. Pfm.), 1897, 1902. And, finally, in 1905 Christensen accepted 
Llavea as a monotypic genus (Index Filicum ), and associated it with Clieilanthes, 
Notliochlsena, Onychium, and Cryptogramme. 
This plant has never before been submitted to a detailed examination, and little 
