nature of the vegetation. On exposed ridges and steep, exposed slopes 
it is decidedly less mesophytic and more tropophytic, although it is rare 
to find trees entirely without leaves. Box canons and springy, protected 
slopes show delicate mesophytic plants. 
4. Because of the unstability of the topography, the luxuriance of the 
vegetation is not as great as that which, were the physiography more 
stable, the climate would lead one to expect. 
V. THe EUGENIA-VACCINIUM FORMATION. 
This formation includes that portion of the mountain lying above the 
900-meter contour line. 
Climate.—Its climate is distinguished from that existing below by two 
distinct features which, so far as plant life is concerned, are antagonistic 
to each other. These are strong winds and a much higher relative 
humidity. The former give rise to the peculiar, dwarfed condition of 
the tree growth, the latter to the abundance of epiphytic vegetation. 
The influence of strong winds on the arborescent vegetation on the rim 
of the crater and on the main ridges leading to .it is especially well 
marked. Here, under these conditions of exposure, the vegetation receives 
the full effect both of the northeast monsoon blowing across Manila Bay 
and of the southwest one from the China Sea. A more detailed account 
of the effect of these winds will be given after the vegetation of the 
mountain top has been considered. 
The fact that the relative humidity is higher in this situation, is made 
evident by the frequent fogs which at night, as a general rule, hang over 
the top of the mountain. The following readings, taken on clear days, 
were made simultaneously at Station 3 and at various altitudes on the 
main ridge: 
TaBLE XXI.—Relative humidity at different altitudes on Mount Mariveles, 
| Altitude. | 
i : | Sian IEEE a 
1966. moer | 640 gl4 1,066 1,250 | 
| meters. | meters. | meters. meters. 
Oe ee en dat «ah es 9.00 a.m, 91 
12.30 p. m. | 77 
a sn rapid ow ev ead wim cook lah 7.30 a.m. | 81 
12.30 p.m. 75 
RMN shite id antcvgegtsea waka att a as 8.30 a.m. 77 
3.10 p.m, 52 
EE ee eee eS 
3.00 p.m. 62 
EA Soli Na tit Sines ua xcals sa hint mnes esac 8.20 a.m. 7d 
| 9.20 a.m. 75 
TNE SCARED dae IL ORI: Be ee a | Oem oy ee es 76. Uist 
1.30 p.m, | Oh Wit ees | Pye (oP) ood Sek 
BEN rece etakent «ckipraddengandamareentomces | 9.00 a.m. Th, Sibeeees eae 1B Scares 
10:00 a.m, | 716 Mle (Sa 8b! ae os 
pt eg: Pee et ee ee ae ee ee | 8.30 a.m. | Ob. iis ee OF eee 8 
| 9.30 a.m, 86 Wes wsdesh ok cnce 83 
| 
AVeTees OFS TOAGiInee. Wo -e 73.8 | Tie eben soe 5 ee ee 
Average of 5 readings-_.-__.______..__.._______ | 82.4 
| ---------- St ee ae 
Average of 2 readings __-.--....-..._.____.________ : 80.5 — | &6 
