Sykes. — The Anatomy and Morphology of Tmesipteris . 67 
branch trace is formed by the passing out of a whole group from the stem, 
its place being subsequently taken in the stem by a group formed by 
division from one of the others. 
The various authors agree that in each fertile branch three bundles 
are finally found, one of which supplies the spore-producing organ, while 
the other two form the traces of the two leaves. Dangeard described the 
forking of the bundle supplying the synangium, but does not appear to 
have carefully traced its course. 
Both the rhizome and aerial stem are said to grow from a single 
apical cell . 1 
Some abnormal fertile branches have been described by Thomas 2 , 
and the development of the spores has been studied by Bower 3 . The 
whole question of the morphology of the fertile branch in Tmesipteris is 
one of considerable difficulty, and its discussion will be reserved for the 
final section of this paper. It must suffice here to state that general 
opinion regards the ‘ synangium ’ as a septate sporangium. 
IV. Internal Anatomy. 
(a) The rhizome grows by a single apical cell in the ordinary manner. 
Cross-sections very near the tip of the rhizome show the following structure 
(Fig. 1, PI. VII):- 
The epidermal layer is thin-walled, and some of its cells are prolonged 
into rhizoids. The cortex is composed of from seven to twelve layers, 
among which three zones can often be distinguished ; the outer and inner 
zones being composed of starch-containing, and the middle of fungus- 
containing, cells . 3 The innermost layer but one of the cortex is impregnated 
with a brown substance which is not soluble in phloroglucin . 3 There is 
a well-marked endodermis, the cells of which have characteristic thickenings 
on their radial walls. Inside the endodermis are four or five layers of 
elongated thin-walled cells which show no marked differentiation into peri- 
cycle and phloem. In the centre of the stele are from two to five tracheides, 
none of which is clearly marked off as protoxylem. Longitudinal sections 
show that all these tracheides are scalariform, including even the single, 
youngest, hardly lignified element at the apex. At this stage there are no 
fibres in the phloem and none of its elements are lignified. Each of the 
cells of the phloem is elongated, with pointed ends, has pitted areas on 
its lateral walls, and contains a large granular mass which gives proteid 
stains and is probably the nucleus. 
If a series of cross-sections be cut, it is found that as one leaves the 
apex of the rhizome the tracheides increase in number and the stele 
becomes bipolar with two exarch protoxylem groups, each of which is 
1 Thomas, 1902. 2 Bower, 1894 and 1903 ; Jennings and Hall, 1891. 
3 Dangeaid, Le Rot, ii, p. 223 ; Miss Ford, 1904. 
