NEW PHYTOIiOGIST. 
Vol. VI., No. 6 & 7. 
June & July, i 907. 
LECTURES ON THE EVOLUTION OF THE 
FILICINEAN VASCULAR SYSTEM. 1 
By A. G. Tansley, M.A. 
(Lecturer on Plant Anatomy at University College , London). 
LECTURE IV. 
-The Gleicheniace-e and Lindsaye-e. 
[Figs. 34—46.] 
We must now consider the Gleicheniaceze, 2 a family repre¬ 
sented by the very characteristic genus, Gleichenia. Two of the most 
aberrant species are sometimes separated as distinct genera— 
G. (Platyzoma) microphylla from North Australia, and G. (Stroma- 
toptcris) moniliformis from New Caledonia. Both are very 
xerophilous and distinctly reduced species. Of the two, Platyzoma 
has the more aberrant vascular system. Like the Hymeno- 
phyllaceae, the Gleicheniaceae are mainly tropical in distribution, 
but the different species are adapted to a much greater variety of 
habitat, some being quite xerophilous while others are shade plants. 
G. linearis (dichotoma) is one of the most widely spread and 
successful of tropical ferns, constantly covering the cleared edges 
of forests, roadsides, etc., with a thick, almost impenetrable growth 
of freely branching fronds. 
The great characteristic of the fronds is their so-called 
“ dichotomous ” branching. The petiole forks into two equivalent 
branches; each branch may again fork into two, and so on. Pinnae 
are borne either by all the branches of the rachis (Sect. Holoptery- 
giurn of Diels) or by the ultimate ones only ( Acropterygium ). A bud 
is very often borne in the angle of each fork of the rachis, and 
this bud (especially that of the primary fork) may grow out and 
form a continuation of the rachis below. These buds are frequently 
spoken of as “ adventitious,” but there seems to be no real reason 
1 A Course of Advanced Lectures in Botany given for the 
University of London at University College in the Lent 
Term, 1907. 
2 The substance of the first part of this lecture is largely based 
on the excellent work of Boodle (’01B). 
