62 
bottom in deep layers for several miles and altogether determines 
the general aspect of the vegetation wherever it occurs. In the 
formation of future strata of the earth’s crust in these regions it 
must become of essential ee, * In tropical regions, 
also, the coralline algae form, in places, a conspicuous part of the 
marine flora, Our plate, XXIV. illustrates one of several forms 
of Goniolithon which are found in the Bahama Islands. In that 
region they grow especially where there are strong sea-currents, 
mostly near the low-water mark or where the water is only two 
or three feet deep at low tide. The form represented in this 
Spi as is very abundant on the windward side of Stocking 
Island, Exuma Harbor, Bahamas, growing chiefly a little above 
the nec mark on rocks which during most of the days of 
the year are subjected to a heavy pounding from the surf. Its 
branches are quite brittle, yet they resist the impact of the waves 
with a success that is surprising. The mass shown in the photo- 
graph (less than half natural size) weighs, with the infiltrated 
sand and a little adherent rock, about es pounds. This perhaps 
pee a single “individual” plant. The Goniolithons, as 
the ur in Bermuda, Florida, and = Bahamas, are commonly 
eae a Lithothamuion tncertum, a Bermudian species, is ordi- 
narily copiously fertile. The small rounded excrescences to be 
seen near the ends of the branches in the photograph of L. zucertum 
(plate X XV) indicate the position of the conceptacles in which th 
reproductive bodies are borne. 
I alay Archipelago, judging from photographs pub- 
lished by Mme. Weber-van Bosse, the coralline algae of the 
Lithothamnion group form beds or banks that are more con- 
spicuous and striking than any that the writer has yet seen 
the West Indian region. In her account of “The Coraline 
of the Siboga-Expedition” (pp. 4 and 5, 1904), she wri 
“Near the coast of Haingsisi, an island near the S. W. ees of 
Timor, the Siboga anchored twice . . .; the second time good 
luck favoured us, it was spring-tide, the water sank very low and 
we could observe that the whole reef, which stretched from the 
*The Algae of the Arctic Sea, 96. 1883. 
