2 9 
Flora of the Ceylon Littoral. 
ever since the first travellers returned from the East. Theo¬ 
phrastus, in his “ Histories of Plants,” describes mangroves from 
the Persian Gulf, apparently from the reports of the officers of 
Alexander the Great. The principal species and their characters 
are noted so exactly that they are easily recognised, and Rliizophora 
is rightly considered the pioneer. 1 The odd thing is that mangroves 
have never since been recorded from this region. 
The genera Rliizophora and Bruguiera (Rhizophoraceae) form 
the great hulk of the typical mangrove forest, and it is naturally 
from them that the popular notions of mangrove vegetation are 
derived. The species of these genera form moderate-sized trees, 
30 to 50 feet in height wh£n well developed, with dark-green 
leathery foliage. The leaves are decussate, petioled, oval, about 
5 inches long, acute or mucronate at the tip, and are typically 
carried so that they diverge obliquely from the stem. 
One of the most striking characters of Rliizophora —the man¬ 
grove tree par excellence —a character which naturally figures 
prominently in the descriptions of travellers—is the abundance of 
branching stilt-roots or “ flying buttress ” roots which spring in 
great numbers from the main stem and lower branches, and form 
an excellent support for the tree against the shocks of wind and 
tide (Fig. 8). These roots not only serve as a support, but are impor¬ 
tant as a means of supplying air to the parts buried in the mud. The 
aerial portion is covered with lenticels which communicate with the 
intercellular spaces of the richly lacunar cortex. Below the level 
of the mud the cortex increases in thickness and has a very spongy 
texture, so that it acts as a reservoir for the air taken in above. 2 
The other striking feature of the typical mangroves is of 
course their so-called “vivipary,” i.e. the fact that the seed 
germinates while on the tree. The hypocotyl increases greatly 
in length and emerges from the fruit, carrying the radicle with it 
and eventually attaining a length of several inches, in Rliizophora 
mucronata sometimes as much as three feet. These long slender 
embryos hang from the branches of the tree “ like candles in a 
grocer’s shop,” as Massart has it. When ripe they are easily 
detached and fall straight down like darts, striking deeply into the 
soft mud, if the tide is low, or falling into the water at high tide 
and often floating away on the ebb. In some species, e.g., R. 
conjugata, the embryo is distinctly club-shaped, so that the lower 
1 Hugo Bretzl. Botanische Forschungen des Alexanderzuges, 
Leipzig, 1903. 
2 See below under Sonneratia. 
