Oil, mineral, [335]

Onayans, the Moro tribe of, [145]

Opium, restrictions on the use of, [630]

Orchids, [323]

Oriente, Islas del, [28]

Origin of Filipinos, [120]. Vide Filipino

Osmeña, Sergio, [521], [524]

Otis, General E. S., in the War of Independence, [488], [490]–[4], [497], [502]–[3]; [563]

Otong, [519] (footnote)

Our Lady of Cagsaysay, [18], [19]