RESULTS, PHYLETIC AND MORPHOLOGICAL 711 
seen living in Z. Seago (see frontispiece, also p. 363): perhaps it may 
ultimately be found to be even better represented by some others of the 
thirty-eight less fully known species of the .Se/ago-Section of the genus. 
The undifferentiated “ Selago” condition, which is seen in them, is no 
recent characteristic, for it appears also in certain Palaeozoic Lycopods: from 
this state the various living forms illustrate the achievement of a more clear 
segregation of sterile and fertile tracts, initiated by abortion of sporangia 
in the sterile regions: along with this goes more adequate protection of 
the sporangia, and their change to a broader form: there is also a greater 
complexity of the stelar structure, and a greater specialisation of the 
embryogeny: the essential parallelism of these progressions indicates that 
they constitute true phyletic lines, the advance having been from the 
primitive condition of the “Sedago” ‘Section to the more specialised state 
of the rest of the genus. The Ligulate series, which includes the most of 
the fossil genera and the modern Selaginella and Jscetes, has as a rule 
more definite heterosporous strobili, though the ‘“ Se/ago” condition is 
again seen in J/soezes, In this respect the Ligulate Lycopods are more 
advanced than the Eligulate. The highest type of propagative organs in 
the whole phylum are the seed-like structures in Lepidocarpon and 
Miadesmia, which show an advance parallel to that found in the Pterido- 
sperms. Both the living and the fossil forms are in their simplest types 
protostelic, but there has been advance to medullation, and finally to 
disintegration of the xylem of the stele and to secondary thickening in the 
dendroid forms. Selaginella Spiniulosa has been recognised among living 
species as a relatively primitive Ligulate type, on the ground of its 
radial construction, its branching, and its anatomy: in these characters, 
as also in point of the embryogeny, S. Spinulosa resembles L. Selago, 
notwithstanding its heterosporous state; this fact has a special interest, and 
the convergence in many features between the two species confirms the 
correctness of their recognition as primitive in their respective genera. 
The Lycopodiales stand by themselves in the simplicity of their 
sporangial arrangement, and constitute a type of extreme antiquity, which 
has come down practically unaltered to the present day. Their comparative 
study may be conducted independently of other phyla: for there is no 
reason to think that they wére derived from any other known vascular 
type. It has been shown that the several lines of comparison converge 
downwards: the condition actually seen in the “Selago” type may be held as 
truly primitive, and Lycopodium Selago, with its imperfectly differentiated 
shoot, is in fact a near approach in a living species to the tdeal primitive 
form which emerges from wide comparative study of the phylum as a whole. 
There are two further characters seen occasionally in the Lycopodiales 
which call for special remark. In the very early fossil, Lycopodites Stockit 
(p. 298), the leaves are arranged in whorls, as they are also in certain 
living species of Lycopodium (p. 291) In others the leaf-arrangement is 
irregular. Sometimes, however, whorled and spiral arrangements may be 
