A small tree 3 to 6 meters in height, with rather open head of short, round or angular branches, thorny; bark grayish; young shoots purplish, smooth; leaves evergreen, alternate, 50 to 75 millimeters in length, ovate oval, sharp pointed, light green, margin serrate; petioles entirely wingless; flowers solitary, occasionally in pairs, axillary, on distinct peduncles; calyx persistent, segments 4 or 5; corolla large, 38 to 50 millimeters across, white inside, purplish outside; petals oblong, spreading, strongly reflexed; stamens 20 to 26, separate, or more or less united in small groups; ovary considerably elevated on a prominent disk, 7 to 10 loculed; fruit ripening at all seasons, ovoid or oblong, and pointed at both base and apex, about 75 millimeters long, smooth or rough, light yellow in color; rind thin, flesh light colored; pulp acid; juice sacs long and pointed; seeds oval, pointed at the micropylar end, quite smooth. Native of the same regions as the citron.
The true lemon is very rarely cultivated in the Philippines and all lemons used are imported from California, Australia and Spain.
Citrus pseudolimonum. Colo-colo.
([Pl. VIIa].)
A thorny shrub, 3 meters tall, with interlocking branches, and short, sharp spines; leaves 8 to 11 centimeters long, 40 to 45 millimeters broad, elliptical to oblong-ovate, crenulate to serrulate; base rounded; apex obtuse, frequently slightly notched; petioles 18 to 25 millimeters long, with narrow wing margin, rarely exceeding 10 millimeters in width; flowers 1 to 5, in terminal or axillary short cymes, 28 to 35 millimeters in diameter, white, purplish outside; calyx cupped; stamens 30 to 37, nearly always free, unequal; ovary broadly obovoid, 14 to 18 loculed; style distinct; fruit roundish to pyriform, small, usually compressed at base; apex irregular; surface greenish lemon, more or less corrugate; oil cells raised; skin comparatively thick; pulp acid; juice cells small, short and plump; seeds undeveloped and sterile.
The colo-colo is another of these peculiar Philippine species with more or less winged petioles affiliated to the lemon, etc. Flowers were collected in May, and ripe fruit has been examined in January and February. The nearly always free stamens in a plant belonging to the same general group as the lemon is of interest.
Near the colo-colo is the “lombog,” considered a distinct fruit, also found in Bohol. This variety is less vigorous than the colo-colo and also differs from the plant in having narrower wing margins and 21 to 28 stamens and 9 to 11 locules. The fruit is said to be about 4.5 centimeters in diameter and similar in shape to that of the colo-colo.
The “kunot” is a third variety considered distinct by the Boholanos that also may be referred to C. pseudolimonum.
To C. pseudolimonum may perhaps also be referred a thorny, arborescent shrub, attaining a height of 4.5 meters, found in Siquijor, a little island south of Negros. Material of this was collected in August, 1912, by the writer, at which time the tree bore partly grown, oblong, rough, small fruits. The plants at Lamao have flowered during the last two months but have not set fruit. The principal difference in this variety from the colo-colo and lombog is in the number of stamens, here 36 to 41.
The fruits of C. pseudolimonum have no economic value.