641 
it should not be represented by more specimens lower down ** and why 
it disappears almost entirely on the ridge leading to Limay Peak is not 
known. The explanation of its scarcity in the latter locality is probably 
correlated with the extension of the Bambusa-Parkia formation higher 
up the mountain in this situation. That the heat of the low country is 
not too great for it to flourish is evidenced by the fact that on the east 
coast of Luzon, where the dry season is less pronounced, it descends nearly 
to sea level. 
The topography of this formation is similar to that of the previous 
one discussed—i. e., it shows alternating prominent ridges and valleys. 
With the exception of its non-occurrence on the steep slopes, where the 
vegetation is thin and in the beds of the river canyons, Dipterocarpus 
itself is not confined to any particular topographic type. At the extreme 
upper limits of the apitong zone is a sharp knob where all the soil has 
been washed off, leaving the half-disintegrated volcanic rock exposed on 
the surface. On this area, out of 60 trees noted, 18 were Quercus sp.; 
11, Vatica mangachapoi; 10, Shorea polysperma; 9, Eugenia pallida; 5, 
Symplocos oblongifolia, and the remainder Dipterocarpus grandiflorus, 
Ternstroemia toquian, Aporosa symplocosifolia, and Plectronia viridis. 
All these species in this situation have much reduced leaves and the 
trees show a tendency to become dwarfed. This plot is the lowest place 
which was observed on the mountain, where exposure to wind dwarfs 
the trees of the forest. The climbing bamboo (Dinochloa tjankorreh) 
is characteristic on the open places on steep slopes. No other bamboos 
are present in the formation. Young trees of the Dipterocarpacee with 
Memecylon edule, Aporosa spheridophora, Diospyros pilosanthera, Uvaria 
alba, Claoxylon rubescens, Codiaeum luzonicum, Leea philippinensis, 
Litsea luzonensis, Dracaena augustifolia, and Tabernaemontana panda- 
caqui form the undergrowth. 
In its response to the xerophytic conditions of the dry season, this 
formation differs from the Anisoptera-Strombosia one in having fewer 
deciduous trees. Isolated specimens of Parkia roxburghti are about the 
only individuals which shed their leaves completely during a portion 
of the dry season, but nearly all the trees show a thinner foliage. 
Dipterocarpus grandiflorus completely changes its leaves during Jan- 
uary and February, but simultaneously with the dropping of the old, 
new ones take their place. At this season of the year the thick bed of 
dead leaves on the ground, the large, red, bud scales appearing with the 
new leaves and the large, sweet-scented flowers of this species accentuate 
its numerical importance. The ground itself is so completely covered 
with fallen foliage that this characteristic, together with the thin under- 
growth, reminds one strikingly of the forests of temperate regions in 
the autumn. Plates XXIV and XXVIII will give some idea of the gen- 
“Only one was noted in the Anisoptera-Strombosia formation and none were 
observed above an altitude of 450 meters. 
43814——5 : 
