Sykes . — The Anatomy and Morphology of Tmesipteris. 87 
The extraordinary resemblance between such a form as Sphenophyllum 
majus , with its lax cone and simple sporophylls, and Tmesipteris , causes one 
to search for some evidence of phylogenetic relationship. In this connexion 
the theory that the sporophyll in the Psilotales is a lobed leaf has received 
much attention. The question is here raised as to whether it is possible 
to look upon the sporophylls in the Sphenophyllums as organs in which 
the branch axis has become much reduced or is wanting, each so-called 
‘ sporophyll ’ being morphologically equivalent to a branch bearing leaves 
and sporangia. 
The similarity found to exist in the methods of formation of leaf and 
branch traces in Tmesipteris is of some interest in a member of Jeffrey’s 
class Lycopsida. The difference is shown to be one of degree only, the 
presence of a gap depending on the greater length of time elapsing between 
the division of a xylem group to form a trace and the departure of that 
trace from the stele, during which time the trace has assumed the appear- 
ance of a separate constituent of the stem stele. Both leaf and branch 
traces are originally formed in exactly the same way, by the division of 
a xylem group of the stem, half the protoxylem and all the centrifugal 
xylem of which becomes surrounded by phloem and give rise to the trace. 
Such facts appear to militate against Jeffrey’s hypothesis of the essential 
importance of gaps. 
Finally, it is concluded that the relationship of the Psilotaceae are 
not sufficiently evident as yet to warrant a position especially near any 
family, and that they are better retained alone in the cohort of Psilotales. 
Literature cited. 
Baker: Fern Allies. London, 1887. 
Berridge, E. M. : On two new specimens of Spencerites insignis, Ann. of Bot, xix, 1905, p. 273. 
Bertrand, E. : Recherches sur les Tmdsipteridees. 1883. 
Boodle, L. A. : Anatomy of Gleicheniaceae. Ann. of Bot., xv, 1901. 
: Anatomy of Schizeaceae. Ann. of Bot., xv, 1901. 
: Note on the lignification of the phloem in Helianthus. Ann. of Bot., xvi, 1902. 
: On secondary tracheides in Psilotum. Ann. of Bot., xviii, 1904. 
Bower, F. O. : A theory of the Strobilus in Archegoniate plants. Ann. of Bot., viii, 1894. 
: Morphology of Spore-producing members. V. Conclusions, Phil. Trans., 1894. 
: Morphology of Spore-producing members, Equisetineae and Lycopodineae. Phil. 
Trans., 1894; II. Ophioglossacea, Phil. Trans., 1896. 
Campbell: Mosses and Ferns. New York, 1905. 
Dangeard, M. P. A.: Mdmoire sur la morphologie et l’anatomie des Tmesipteris. Le Botaniste, 
ii, p. 163. 
