456 WILLIS : MORPHOLOGY OF THE PODOSTEMACEÆ 
Explanation of Plates IV -XXX VIll. 
Note, — In consequence of its having been decided, aHer some of the later 
plates had already been printed, to omit certain anatomical details, it has 
been found necessary to omit Plates XXIII., XXVII., and also the last two 
Plates (already mentioned in the preceding paper; XXXIX. and XL. The 
total number of plates published with this paper is thus 33. 
All drawings and photographs are the work of the author, with the 
exception of fig. 2. PI. XXX.. for which he is indebted to Mr. A. de Alwis. 
It may be noted that the photogravures, being prepared directly from the 
negatives, show much detail, and will bear a magnification of two or three 
diameters under a lens. 
Owing to the great local difiierences in these plants the source of the 
material is quoted in most cases. 
Plate IV. — General view of part of Ilakinda rapids on the Mahaweli- 
ganga near Peradeniya (the background is part of the forest reserve of the 
Experiment Station), showing Podostemaceæ exposed upon the rocks in the 
dry season. 
The island rock in the left-hand bottom corner is covered with fruiting 
Dicræa elongata ; the rock to the extreme left, in the sheltered bay, is 
covered with Podostemon subulatus. To the right of it, in the less rapid 
part of the main current, is Dicræa elongata. The rocks at the little fall 
(which is about 3 feet high) are covered with Hydrobryum olivaceuna, 
while the parts between the fall and the Dicræa bear both this species and 
Lawia zeylanica, as also does the central island. 
Plate V., Tristicha ramosissima ; herbarium specimen prepared by 
Mr. C. A. Barber by floating out under water (material from S. Kanara, 
No. 2,518), X 4/7. This gives a very clear idea of the general habit in the 
vegetative condition ; the creeping root-thallus runs through the middle 
of the sheet, giving off secondary shoots (often paired) with hapterous 
bases, and bearing branches of two kinds, long and short, the latter 
(ramuli) with filamentous leaves. 
Plate VI. — The same. The left-hand specimen shows the branching 
clearly ; at each node two branches, long and short, the latter below the 
former. The right-hand specimen shows the floral and fruiting shoots, 
and the way in which the ramuli lose their leaves at this season. The 
floral shoots have a few leaves at their bases, and a couple of ramuli, and 
stand erect, emerging from the water in which the main shoot is drifting. 
Plate VII., Tristicha ramosissima. — Fig. 1 Portion of thallus 
(th ) attached to rock, showing hapterous discs or feet (/<!.), from which 
the secondary shoots {s.si) spring, x 1^(0. A. B. 2,518). 2 Tip of thallus 
in optical section, showing rcot-cap .(r.c.), X 35 (Anamalai). 3 Rhizoids 
developing from thallus, X 60 (Anamalai). 4 The same against the rock, 
with dark cement secretion. 5 Portion of thallus (fA.) with commence- 
ment of development of endogenous secondary shoots (ä.^s.), X 6 
(Anamalai). 6 The same, later, with hapterous foot (/!.). 7 Transverse 
section of thallus, feet, and secondary shoots, diagrammatic, showing 
endogeny of shoots (^.-?.), and vascular strand (r.&.) with its branches to 
shoots, X 35 (Anamalai). 8 Lower end of a hapteron, showing mode of 
