68 
A. G. Tansley. 
strand of the frond. The leaf-trace of Anachoropteris (Fig. 21) is, 
according to Renault’s account, at first a closed ellipse (A) which 
Fig. 21. Anachoropteris Decaisnii. Leaf-traces showing opening of 
ellipse probably on the abaxial side to form a C. From Renault. 
afterwards opens (B and C) to form a tangentially extended C, 
apparently open on the abaxial side as in Tubicciulis. In Asterochlcena 
(Fig. 22) the lobing of the stele is even more marked, but the leaf 
traces apparently arise each from a single lobe, and are more of 
the Gramrnatopteris- type, so that this genus stands rather apart from 
the Zygopteris-Anachoropteris series. 
Fig. 22. Asterochlcena laxa. Part of transverse section of stem with bases 
of surrounding petioles, showing deeply lobed stele with pith extending into 
lobes and leaf-traces becoming slightly curved arcs in the petioles. From 
Stenzel. 
Thus we see very clearly in the Botryopterideae the beginnings 
of that tendency to basipetal phylogenetic development of the 
vascular system, from the transpiring laminae into the axes of 
the frond and from the frond into the stem, which is really (apart 
from secondary thickening) the leading factor in the evolution of 
the general form of the vascular system throughout the higher 
plants. 
