OP CEYLON AND INDIA. 
273 
the Ceylon species Dicræa elongata and D. algæformis (D. 
stylosa), where the thallus is more or less dimorphic, a part 
of it creeping on the rock and branching in the plane of the 
rock, part of it consisting of long filamentous or ribbon- 
like organs arising from the creeping parts and streaming 
out freely in the water. These thalli are phylogenetically 
of “ root ” nature. On the streaming thalli the secondary 
shoots arise endogenously, as in Podostemon, but are only 
single-flowered and very short. 
In the third paper several species of Podostemon are 
described;, which resemble P. Ceratophyllum in their 
morphology. Some species of Apinagia and Ligea are also 
described, in which there is a more complex shoot than in 
Podostemon, which has many leaves, and drifts out in the 
water, bearing at the usual season a complicated inflorescence. 
The shoot and not the root is the principal growing and 
assimilating part in these forms. Mourera aspera, which 
has a sort of rhizome, bearing large leaves and complex 
inflorescences, is then described. 
The fourth paper deals first with the curious African genus 
Hydrostachys, which Warming has since placed in a separate 
family. The Abyssinian form Sphærothylax (Anastrophea, 
Wedd.), which has both a flat lichen-like thallusand a tall erect 
stem, is then described. The thallus is shown to be of “ root ” 
nature like the thallus of Podostemon, and it bears small 
endogenous flowering shoots all over its surface. This very 
remarkable structure is repeated in Hydrobryum olivaceum, 
a Ceylon species described in the same paper, only that here, 
so far as Warming’s observations (made on spirit material 
collected in the dry season) show, the plant has only the 
thallus, and thus practically consists of a ‘‘root ’’alone ; this 
is, as we shall see, not quite the case, but the tall primary 
axis when seen in 1854 was mistaken fora distinct species, and 
received the name Podostemon Gardneri. This very curious 
plant is also described by Warming in an earlier part of the 
same paper under the name of Dicræa apicata of Tulasne. 
The full life-history is given below. Prof. Warming 
