192 The Philippine Journal of Science 1917 
but apparently must be referred to unfavorable external condi- 
tions. These factors will be considered later. 
SHORE VEGETATION 
‘One of the most interesting features in the distribution of 
plants on the island is that of Ipomoea pes-caprae. This plant is 
a spreading vine, which usually forms a part of the strand 
formation on sea beaches. It occurs as occasional patches on the 
mainland shore of Lake Bombon where it is sometimes’ mixed 
with Canavalia lineata, a leguminous species of similar habit. 
While the leaves of Canavalia are compound and those of I[po- 
moea are simple, nevertheless the texture and the color of the 
leaflets of Canavalia and of the leaves of Ipomoea are so similar 
_ that it is only by the flowers that the two plants can be readily 
distinguished at a distance. These two plants occur together 
in scattered localities along the shore on all sides of Volcano 
Island, but they are more conspicuous on the slopes inland 
from the southern and southeastern shores. They have ap- 
parently grown over the ash on the southern coast to an altitude 
and distance as limited only by the period during which growth 
has taken place. Both have reached a vertical height above the 
lake of more than 50 meters, while Ipomoea is prominent more 
than 0.25 of a kilometer from the coast. Over large stretches 
of the lower ridges near the coast Ipomoea forms a thick carpet 
between the clumps of Saccharum. As the Saccharum becomes 
denser, it will probably replace the Ipomoea; as along the 
northern coast, where the growth of Saccharum is thicker, Ipo- 
moea pes-caprae is confined to the beach and does not occur 
inland. 
Ipomoea is particularly abundant near the southern and 
eastern coast and on the peninstla that extends from the south- 
western corner and to a-less extent around the base of Mount 
Binintiang Malaqui. Except in the two last-named regions 
Ipomoea and Canavalia are represented on the western coast by 
only a few scattered plants. This is apparently due to the 
presence of numerous wide deltal fans on this side of the island. 
In Plate IX, fig. 1, Ipomoea is shown growing near the water’s 
edge, but more abundantly on the more elevated ground where it 
‘is mixed with Saccharum. Ipomoea grows on the mainland in 
an area made swampy by fresh-water springs. This distribu- 
tion is apparently not connected in. any way with a nigh salt 
content of the soil. 
