OF CEYLON AND INDIA. 
353 
and with the explanation that accompanies it is sufficient to 
clear up the somewhat confusing appearance of the various 
existing specimens of this species and its synonym. 
The thallus grows by a broad growing point like that 
described below in D. stylosa fucoides, with exogenous 
branching; it forms endogenous secondary shoots on the 
upper edges, to which run branches of the Central vascular 
bundle (PI. XX., fig. 11). Probably when in full vegetative 
growth in September the plant is very like D. stylosa 
fucoides as shown in PI. XXII., fig. 3, but towards the end of 
the season the tips of the thallus lobes are commonly found 
to have fallen away or to be breaking off, so that the general 
form is commonly like that shown in fig. 12, PI. XX. In 
this specimen the vascular bundles are shown, leading to 
the marginal secondary shoots (themselves not shown). 
Ultimately, as usual, some but rarely all of the secondary 
shoots become floriferous, and here a peculiarity of this 
species shows itself, in that instead of the flowers being 
concentrated on one part of the thallus, they are scattered 
over the whole or most of it, in each lobe some of the shoots 
becoming floriferous, the rest remaining sterile. Round the 
vascular bundles leading to the developing flower the tissue 
as usual becomes thick-walled and brown, while the bundles 
leading to the sterile shoots are not so surrounded. The 
former bundles show clearly as brown bands through the 
living thallus fig. 13). As the flowers develop the inter- 
mediate tissues become disorganized and begin to break 
away, so that finally nothing is left but the brown bands of 
thick-walled tissue containing the vascular bundles leading 
to the flowers. Thus the remarkable differences seen in the 
different collected material are easily explained. The 
process is not usually complete till the plant is fully exposed 
on the rock, and I am inclined to think, but cannot be sure, 
that the flowers emerge from the water as soon as it gets 
shallow. Griffith’s material mostly shows the thallus with 
the thin marginal parts between the bundles still present, 
though the fruits are ripe. Other material has been 
