cclxxxi 
Actinoids. KADIATA. Aotinoids. 
the branch Corals wliich lias been left denuJecl of 
flesh (lies, and is easily broken by the waves. 'I’he 
Coral-eating' Fishes crash the delicate branches, and 
great quantities are thus thrown down to add to the 
general mass. In this way the bottom of the ocean 
has received an additional quantity of material, and 
the distance between that and the surface is constant- 
ly lessened. The ratio is rapidly increased as it goes 
on, for there are new elements introduced at every 
turn. The smaller species of Corals — those that re- 
quire protection — are ready to take root, as it were, 
and are seen sprouting out in all directions; these 
also add by their bulk to the general amount. Shell- 
fish of various kinds take up their abode here, as well 
as the Hermit and other species of Crabs, together 
with Worms innumerable ; the softer and particularly 
the dead Corals are found riddled by the latter. The 
Date-clam is a common source of destruction to the 
blocks. If we break open a block of dead Coral, it 
will be found nearly occupied by Worms, boring 
Shell-fish and Echinoderms. d’hese tend to break 
up the great masses that eventually spread out to 
make up the general quota, wdiich, as it gradually 
reaches the surface, meets other elements entering 
into its growth. 'I’here are many kinds of Cora.1 
which are so delicate that they will not grow unless 
protected from the rude rush of waters, and these 
are seen to ta.ko place in the shallow lagoons or 
bays which are formed when the Reef has grown 
up to near the suiface of water; when within a few 
inches or feet, the Alga3 and the Corallines are added. 
All these help in the great work, as every particle of 
refuse matter from them is so much more towards 
the aggregate. When the Reef has nearly reached 
the surface, the water is too shallow for the Corals 
to flourish in ; some other element, then, is requisite 
for securely holding the top dressing or first dry 
layers of the new island. Here Nature would seem 
to have provided means of a wonderful character to 
Fig. xii. 
Mangrove Trees, Elongated Bnda and Young Trees. 
meet the situation. The Mangrove-tree (fig. xii) is 
adapted to this work of finishing the Reef. 'I’liis is a 
small shi'ub-like tree, furnished with a, p(muliarbud or 
VoL. I. — n* 
fruit (fig. xiii), which is capable of elongation so as to 
touch the Reef. This bud is germinated prematurely 
in the flower, and the fruit grows to the size and shape 
of a cigar ; indeed, they so closely resemble a cheroot 
that strangers are frequently d(;- 
ceived when they see them floating 
in the sea. 'I'he buds are cast off 
in large numbers by the trees, and 
the latter being always near the 
water or overhanging it, the for- 
mer float in the sea. Now, when 
the buds reach the shallow water 
covering the Reef, which we have 
seen growing gradually up by ad- 
ditions of dead and living Corals, 
the larger end of the bud, being 
heaviest, is stranded in the sand 
or mud, and sends out shoots 
which prove to be little roots. 
During the still, warm weather of 
midsummer, these little trees in 
miniature take root and become 
fast in the soft mud, and soon 
grow to be trees. A few leaves 
shoot forth, and the rootlets at the 
lower end soon throw out more 
branches, wliich serve as braces, 
so that when the winds of winter 
come there is little danger of their being disturbed. 
.Myriads of these Mangrove shoots are in this way 
propagated. 'I’he great swamps of the everglades are 
thus having a constant addition to their boundaries. 
'I’he Mangroves being once established, and the 
outlying shoots put forth, there is a steady accumu- 
lation of floating weeds and the natural waste of the 
sea. This material is entangled, and gives opportu- 
nity for the same to gather around the roots, and, 
with the aid of all the elements introduced, the surface 
of the sea is soon reached. The influence of the tide 
and winds alters somewhat the face of the surface, 
but the accumulation is sure to produce a firm base, 
on which the seeds of plants take root’. Nature 
furnishes suitable plants for the purpose. On the 
Keys a large species of Convolvulus is found, throw- 
ing out long and tough runners which take root at 
certain intervals, and thereby afford a resting-place 
for the drifting sands ; while other and more delicate 
plants find a footing. AVe have now a Reef made 
upon a solid stone basis, and a soil fitted to receive 
certain plants which serve to augment the chances 
of a more varied growth. On some of the older Keys 
there are trees eighty feet in height, and a large 
variety of smaller kinds. 'I’hese older islands have 
in many cases a thickness of soil equal to several 
feet, entirely made up by the continual growth and 
decay of vegetable and animal forms. 
Professor Agassiz considered that the growth of 
Coral Reefs only reached a fraction of an inch in a 
number of yeai's. This estimate of the rate was in- 
correct, we think, from our observation of the growth 
of the Madrepores, which during a single winter was 
seven or eight inches above the lowest fide. When 
the low tides have exposed the living Corahs, there 
Fig. xlii 
Mangrove Bud 
taking root. 
