WILLIS : MORPHOLOGY OF THE PODOSTEMACEÆ 
Oioræa s^inor^ Wedd. 
(Plate XXIV.) 
As mentioned in the preceding paper, the autonomy of 
the species is very doubtful, and further investigation on 
the spot where it grows is required. Griffith’s dry material 
looks distinct, on account of the very short fruit stalk (PI. 
XXIY., fig. 6), but the spirit material collected at Nongkhlaw 
by Sir J. D. Hooker, and named by Weddell, looks to me 
very like D. Wallichii, though of course, having been collect- 
ed in a different locality from the typical D. Wallichii, it 
will probably prove different in detail. A specimen is 
figured in PI. XXIY., fig. 4, and a flower bud (secondary 
shoot) in fig. 5. In view of this uncertainty there is no 
need to describe it further. 
Comparing Dicræa with Tristicha and Podostemon, it is 
evident that at least one line of evolution which was pointed 
at by a comparison of those genera between themselves has 
here been carried out much further, viz., the dwarfing and 
reduction of the size of the individual secondary shoots. In 
Dicræa they are very small, with no appreciable axis until 
they flower, and the number of fl.owers on each is still further 
reduced than even in Podostemon, each shoot bearing one 
only. The number of shoots, on the other hand, is so greatly 
increased that, though only part of them flower, the number 
of flowers is probably about as large as in Tristicha or 
Podostemon. The advantages gained by the reduction of 
the size of the shoots are evident ; the plant is able to live in 
shallower water, and it suffers less from exposure resulting 
in the death of the exposed shoots ; instead of losing a large 
and complex shoot as happens in Tristicha and to a less extent 
in Podostemon, it loses only a few leaves, and the small 
portion of thallus on which they stand or which may be 
exposed ; at the same time this thallus retains its vitality 
for a considerable period, and may revive and form new 
