ik 
204 The Philippine Journal of Science _ 1917 
and the floor of the crater, as viewed from about the southern- 
- most point of the rim. : 
The preceding discussion shows very clearly that the revegeta- 
tion of Volcano Island is proceeding in a very different manner 
and much more slowly than does the revegetation of land from 
which forest has been removed by logging. We have seen that 
the first invaders of the latter areas are tree species, and in two 
or three years the land is covered by a forest composed of small 
trees. The specific composition of the latter forest is very dif- 
ferent from that of the original. 
As has been shown, it would seem that both the slow reveg- 
etation of Volcano Island and the scarcity of trees should be 
attributed to adverse environmental conditions rather than a 
lack of seed. 
COMPARISON WITH KRAKATAU 
The early stages in the revegetation of Volcano Island have 
been very different from those on Krakatau. Treub,”4 who vis- 
ited Krakatau three years after the destruction of the vegetation 
of that island, found that the new vegetation could be divided into 
two classes ; namely, a strand vegetation, which owed its existence | 
to seeds carried by ocean currents, and an inland vegetation, 
consisting very largely of 11 species of ferns. According to the 
observation of Treub, habitats suitable for the growth of fern 
prothallia were provided by blue-green algae which were very 
prominent in the early stages of revegetation. 
Besides the ferns there were in the interior eight oe of 
phanerograms, two of which also occurred on the strand. The re- 
maining six species, and the previously mentioned ferns were 
apparently carried to the island by wind. No blue-green algae 
have been reported from Volcano Island, and perhaps on this 
account ferns have not been prominent. There are 21 species of 
. Pteridophyta on the island, but these are mostly confined to deep 
ravines and to the sides of cliffs along the shore. They appear 
to be restricted largely to a substratum, which existed previous 
to the eruption of 1911; whereas on Krakatau the ferns were 
growing in new soil. 
There are now 292 species of ferns and seed plants growing 
on Volcano Island. We call attention elsewhere to the fact that 
only a few of these have found a favorable habitat of any con- 
siderable extent as only 13 species are common and widely 
*“Treub, M., Notice sur la nouvelle Flore de Krakatau, Ann, Jard. Bot. 
Buitenzorg 7 (1888) 213. : 
