334 WILLIS : MORPHOLOGY OF THE PODOSTEMACEÆ 
common filament. The ovary is of two carpels, bilocular, 
with a stout axile placenta, thin septa, numerous ovules, and 
two stigmas. In cross section it is very like that of P. Bar- 
beri (PI. XVII., fig. 6), but the outer margin of the deciduous 
tissue is not undulate, so that the ovary is not winged as in 
that species. In all other respects it is the same, and the 
description given below will suffice for both. 
The stamens stand away from the stigmas, so that self- 
pollination is not absolutely inevitable, though it seems by 
far more common than a cross. The flower is anemophilous, 
and produces large quantities of loose powdery pollen. 
Practically all the flowers appear to set a full complement 
of seed. The seeds are very small and soon ripe. 
The development of the fruit is of particular interest, and 
as it is very similar in all the following genera, it will save 
repetition to describe this one in full. As in most of these 
plants, the seed is practically no larger than the ovule, and 
the fruit than the ovary, as is shown in PI. XVI., figs. 10, 12, 
and 13, which are all on the same scale. The pedicel, as 
already described, has a thick cortex, which, as in Lawia, is 
deciduous, leaving the now woody central tissue as a slender 
but much more elastic stalk to the ripe fruit. With this 
deciduous tissue there falls away also the outer tissue of the 
ovary, as indicated for P. Barberi in PI. XVII., figs. 6 and 9, 
leaving to the ripe fruit only the vascular tissues, which 
become strongly lignified and form the ribs, and the inner- 
most two layers of cells, already cutinized in the ovary, 
which form the wall of the ripe fruit, and are very smooth 
and shiny within, but rougher on the external surface where 
the other cells have fallen away. The outer layer of the two 
also becomes strongly lignified. The ripe fruit is thus, if 
anything, rather smaller than the ovary, but with clearly 
marked ribs. 
The distinction between the genera Podostemon and 
Dicræa is partly based on the mode of dehiscence. In the 
former the two lobes are unequal, and one falls away leaving 
the other on the stalk, while in the latter both are equal and 
