460 WILLIS : MORPHOLOGY OF THE PODOSTEMACEÆ 
splitting layer. 8 Transverse section of the inner epidermis of the fruit, 
to show construction of the wall, x 320. 9 The fruit, in transverse 
section, x 60, for comparison with fig. 6 ; the outer tissues have fallen 
away, and the rest have become woody. 
Plate XVIII., Dicræa elongata. — 1 Seedling, x 6, showing com- 
mencement of thailus (^^.). 2 Larger seedling, X 6, showing development 
of first free drifting thallus (dr. th.') from the creeping thallus. 3 Base 
of seedling, X 40, showing cotyledons (cot.')^ endogenous thallus and 
exogenous hapteron (h.'). 4 Seedling, x with drifting thallus form- 
ing at right angles to creeping thallus ; the primary axis. 5 Apex 
of drifting thallus, X 5, with root-cap and origin of secondary shoots. 
6 Transverse section of drifting thallus, X 20, showing parenchymatous 
cortex (p.c.) and vascular bundle (v.h.'). 7 Cortex of drifting thailus in 
transverse section (taken about middle of length, 1-9-98), X 80, show- 
ing commencement of cell division. 8 Transverse section of vascular 
strand, near apex of drifting thallus, gathered 1-9-98, X 320 ; X, primary 
xylem ; col.^ collenchyma. 9 A small part of the same strand, lower- 
down, X 320, showing commencement of formation of secondary tissue. 10 
The same, older, x 320, with formation of secondary xylem nearly com- 
plete. 11 Transverse section through thallus at exit of secondary shoot, 
X 16. F.&., the vascular strand with branch to shoot ; col., the collen- 
chymatous layer ; d.c., the part of the cortex which finally shrivels ; v.a., 
the growing point of the shoot ; 1., its leaves. 12 Transverse section of 
ovary, X 60, for comparison with Podostemon ; i.e., the iuner epidermis ; 
■o.h., the vascular bundles. 
Plate XIX., Dicræa elongata, x 3/8. — On the left fruiting specimens 
from Hakinda, gathered in dry season. On the right a plant in water, 
gathered in September in vegetative condition, showing the creeping 
thalli at base, with long drifting thalli, along whose edges are the little 
tufts of leaves representing the secondary shoots. 
Plate XX., Dicræa elongata. — 1 Piece of thallus, x 4, showing re- 
juvenescence from the base of an old portion re-submerged ; th., creeping, 
dr.th., drifting thallus. 2 Fruit, X 6, for comparison with that of 
Podostemon (PI. XVI.), to show isolobous development and mode of dehi- 
scence. D. dichotoma. — 3 A small piece of thallus and secondary shoots, 
to show zigzag form often assumed. 4 Transverse section of thallus in 
flowering season, x 20, to show deciduous (dec.^ and persistent (pers.) parts 
of cortex ; v.h., the vascular strand. 5 Portion of flowering thallus, 
showing projections under the floral shoots, X 1^. 6 Secondary shoot, 
X 2, in leafy condition, just beginning to form a flower. 7 Later stage, 
with spathe (s^a.} visible between upper pair of leaves with enlarged 
sheathing bases. 8 Later stage, with leaf tips falling away. 9 Flowering 
shoot, with bracts at base whose leafy tips have completely fallen ; spathe 
open, flower fully expanded. 10 Fruit, X 6. Dicræa Wallichii.— 11 A 
portion of a plant from herbarium material, X 3, showing form of growing 
apices, and development of the secondary shoots, with vascular bundles 
(v.h.'), the latter thickened where they lead to shoots, about to bear flowers. 
12 A small portion of the base of a plant (Cherra), X 2, showing vascular- 
bundles before the beginning of development of flowers. 13 The same 
after development of the flowers (these not shown;. 14 Base of a plant 
