408 The Philippine Journal of Science 1914 
limit is usually other vegetation, but in case there is no other 
vegetation, Canavalia tends to extend inward away from the 
water to a very much greater extent than Ipomoea, which is 
usually confined to the shore. Exceptions occurred on the lava 
ridges of Mount Binintiang Munti, where Ipomoea spread a 
considerable distance from the shore, and in a few places on 
the eastern side of the island, where unaccompanied with Cana- 
valia, Ipomoea spread back several meters and attained an 
altitude of about 30 meters on the mud slope. 
The ridges which separate the low deltal flats from Lake 
Bombon are sometimes vegetated with this association but more 
frequently are bare. Except in extremely sheltered coves or 
bays, secondary species were absent from this association. In the 
bay near Pirapiraso, where Ipomoea was barely holding its own, 
there were many secondary species, most of which were weeds, 
as Ricinus communis, Datura alba, Bulbostylis barbata, Eleusine 
indica, Wedelia biflora, Amaranthus spinosus, Ipomoea pes-tigri- 
dis, Ipomoea triloba, Hewittia sublobata, Eclipta alba, Leucas 
javanica, Portulaca oleracea, Heliotr opium indicum, Scoparia 
dulcis, Polanisia viscosa, Dactyloctenium aegyptium, Citrullus 
vulgaris, Digitaria consanguinea, and seedlings of Acacia farne- 
siana. These were all jumbled together, as though many seeds 
had started to grow at one time, but the typical adjustments had 
not yet taken place. 
Over much of the area little successional relationship was ex- 
hibited in relation to this association, for the areas occupied by 
other plant associations were noncontiguous with that occupied 
by this one. The Ipomoea association, therefore, was limited 
in extent only by the physiological requirements of the individual 
plants. Where the shore was narrow and the upward slope 
abrupt, this association was succeeded by the cogon association, 
whose grasses quickly shaded the Ipomoea out of existence. Ca- 
navalia responded for a while by growing up into the grass, 
but ultimately gave way also. 
THE SESBANIA STRAND ASSOCIATION 
A back strand association, which also occurs along Lake Bay 
to the northeast, is present along the west coast of Taal Island 
at the foot of Mount Binintiang Malaki and, to a more limited 
extent near the foot of Mount Balantoc. Although not extensive 
it is entirely normal, consisting of open bushes of Sesbania can- 
nabina, with no secondary species here represented. It is readily 
and rapidly invading the Ipomoea pes-caprae association back 
