39 
Flora of the Ceylon Littoral. 
and Acanthus and of the pneumatophores of Sonneratia. We have 
observed these Algae in almost every locality in Ceylon, where the 
above-mentioned genera are to be found, although where the 
mangroves are rare, the Algae are still rarer ; thus at Kalutara the 
typical algal forms were only found after a lengthly search, whilst 
at Matara they were not discovered at all. Their absence is in 
part undoubtedly connected with the weak development of the 
actual mangrove element, but in part it would certainly seem to be 
due to the muddy character of the water; the rivers at Kalutara 
and Matara are both very turbid—at least at the time of the 
year at which we saw them—whilst the river at Bentotta is rather 
clearer and here mangrove : Algae were observed in considerable 
amount. In the lake at Ambalangodda, in which the mangrove- 
element is quite wanting, none of the typical algal forms were 
observed, whilst in the lake at Panadure the latter were found on 
the roots of the Rliizopliora and Acanthus occurring there. These 
few remarks will suffice to show that wherever the mangrove- 
formation is at all well developed we meet with these Algae in 
connection with it, so that they must be regarded as an essential 
feature of this formation. 
The species of Algae concerned belong in the main to the red 
and green groups, although a considerable part is also played by the 
blue-green element. The red forms belong to at least three 
distinct species (apparently Delesseria Caloglossa Leprieurii and 
two further species, which may be provisionally referred to the 
genera Ncnialion and Polysiphonia ; we are not in a position at 
present to publish the specific determinations) and one of these at 
any rate (viz. Delesseria, Leprieurii) was found in every locality where 
these Algae were typically developed. In clear water these forms 
are to be found covering the submerged parts of the stilt roots of 
Rliizopliora to a depth of a foot or more below the surface, but in 
turbid water they are generally confined to within a few inches of 
the water-level, or they may be wanting altogether on most of the 
Rhizophora-voots. In these cases one generally finds an algal 
covering of another kind, consisting of green and blue-green forms, 
either below the belt of red forms or occupying the whole sub¬ 
merged surface of the root; the root then appears thickly coated 
with a dull green or brown fluffy covering, owing to the consi¬ 
derable percentage of muddy particles intermingled with the 
Algae. The most important green forms are a broad-celled species 
of Conferva, and a Spirogyra (the latter at Kalutara), with which a 
