The micrantha is a wild

citrus ''Citrus'' is a genus of flowering trees and shrubs in the family Rutaceae. Plants in the genus produce citrus fruits, including important crops such as oranges, mandarins, lemons, grapefruits, pomelos, and limes. ''Citrus'' is nativ ...

from the papeda group, native to southern

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, particularly islands of

Cebu Cebu ( ; ), officially the Province of Cebu (; ), is a province of the Philippines located in the Central Visayas region, and consists of a main island and 167 surrounding islands and islets. The coastal zone of Cebu is identified as a ...

and

Bohol Bohol (), officially the Province of Bohol (; ), is an island province of the Philippines located in the Central Visayas Regions of the Philippines, region, consisting of the island itself and 75 minor surrounding islands. It is home to Bohola ...

. Two

varieties Variety may refer to: Arts and entertainment Entertainment formats * Variety (radio) * Variety show, in theater and television Films * ''Variety'' (1925 film), a German silent film directed by Ewald Andre Dupont * ''Variety'' (1935 film), ...

are recognized: small-flowered papeda (''C. hystrix'' var. ''micrantha''), locally known as ''biasong'', and small-fruited papeda (''C. hystrix'' var. ''microcarpa'') or ''samuyao''. Although long viewed as a separate species, ''C. micrantha'', it is now generally viewed to fall within '' Citrus hystrix'', but genomic data on the latter is insufficient for a definitive conclusion. A micrantha was one of the

progenitor In genealogy, a progenitor (rarer: primogenitor; or ''Ahnherr'') is the founder (sometimes one that is legendary) of a family, line of descent, gens, clan, tribe, noble house, or ethnic group.. Ebenda''Ahnherr:''"Stammvater eines Geschlec ...

species of some varieties of lime.

Description

The micrantha was first described to Western science in 1915 by Peter Jansen Wester, who worked for the Philippine Bureau of Agriculture at the time.

Biasong

Wester collected ripe fruit specimens of biasong (small-flowered papeda, ''Citrus hystrix'' var. ''micrantha'') on islands of Cebu, Bohol,

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Negros Negros (, , ) is the fourth largest and third most populous island in the Philippines, with a total land area of . The coastal zone of the southern part of Negros is identified as a site of highest marine biodiversity importance in the Coral Tr ...

, and in the Zamboanga and Misamis provinces in

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. The fruits were collected throughout the year, indicating that the plant is ever-bearing. Biasong is characterized by small flowers (thus the "small-flowered" moniker) with fewer

stamen The stamen (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filament ...

s than other papedas and oblong-obovate, few-

locule A locule (: locules) or loculus (; : loculi) is a small cavity or compartment within an organ or part of an organism (animal, plant, or fungus). In angiosperms (flowering plants), the term ''locule'' usually refers to a chamber within an ovary ...

d fruits. Though the fruit is not eaten and with little economic importance, its juice is used as a souring agent for

kinilaw ''Kinilaw'' ( or , literally "eaten raw") is a raw seafood dish and preparation method native to the Philippines. It is more accurately a cooking process that relies on vinegar and acidic fruit juices (usually citrus) to denature the ingredi ...

, or for hair-washing. Biasong's aroma is similar to that of the samuyao variety of micrantha. The tree reaches in height. Leaves are long, wide, broadly elliptical to

ovate Ovate may refer to: * Ovate (egg-shaped) leaves, tepals, or other botanical parts *Ovate, a type of prehistoric stone hand axe * Ovates, one of three ranks of membership in the Welsh Gorsedd * Vates or ovate, a term for ancient Celtic bards ...

, crenate, thin, with base rounded or broadly acute; apex acutely blunt pointed. Petioles are long, broadly winged, up to wide, with wings (phyllodes) sometimes larger than the leaf. Flowers are small, four-petaled, white with a thin purple edge, in diameter, forming

cymes In botany, an inflorescence is a group or cluster of flowers arranged on a plant's stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a main axis ( ped ...

of two to five. There are 15 to 17 equal

s. The ovary is obovoid, with 6 to 8 slender, distinct

s. Fruits are

obovate The following terms are used to describe leaf morphology in the description and taxonomy of plants. Leaves may be simple (that is, the leaf blade or 'lamina' is undivided) or compound (that is, the leaf blade is divided into two or more leaflets) ...

to oblong-obovate, long, with diameter of , averaging in weight; their skin is rather thick, lemon-yellow, fairly smooth or with transverse corrugations; the pulp is juicy, grayish and acid, while juice cells are short and blunt to long, long, slender and pointed, sometimes containing a minute, greenish nucleus. They have numerous flat, pointed,

reticulate Reticulation is a net-like pattern, arrangement, or structure. Reticulation or Reticulated may refer to: * Reticulation (single-access key), a structure of an identification tree, where there are several possible routes to a correct identificati ...

seeds.

Samuyao

Wester collected ripe samuyao (small-fruited papeda, ''Citrus hystrix'' var. ''microcarpa'') fruit specimens from cultivation in Cebu and Bohol in June, and from November to February. Samuyao is rather smaller than biasong, with trees attaining 4.5 meters. It has small, thin leaves and flowers comparable in size to biasong. The fruit, 15–20 mm in diameter, is likely to be the smallest in the whole genus. Wester also recorded a somewhat more vigorous variety, called "samuyao-sa-amoo" in Bohol, with slightly larger fruits; there is a possibility that this species was actually ''Limonellus aurarius'', described by

Georg Eberhard Rumphius Georg Eberhard Rumphius (originally: Rumpf; baptized c. 1 November 1627 – 15 June 1702) was a German-born botanist employed by the Dutch East India Company in what is now eastern Indonesia, and is best known for his work ''Herbarium Amboinense ...

back in 1741 in a nearby area, although his description also fits a number of related species. Wester gave the botanical description: Clear, intensely fragrant oil can be produced from the samuyao peel, and it has been used as a hair fragrance by women who live where it grows.

Toxicity

The micrantha contains a significant amount of

bergapten Bergapten (5-methoxypsoralen) is a naturally-occurring organic chemical compound produced by numerous plant species, especially from the carrot family Apiaceae and the citrus family Rutaceae. For example, bergapten has been extracted from 24 ...

, a linear

furanocoumarin The furanocoumarins, or furocoumarins, are a class of organic chemical compounds produced by a variety of plants. Most of the plant species found to contain furanocoumarins belong to a handful of plant families. The families Apiaceae and Rutacea ...

well known for its phototoxic effects. Of 61 ''Citrus'' varieties tested, ''C. micrantha'' had the highest concentration of bergapten of any ''Citrus'' species. In particular, ''C. micrantha'' contained almost twice as much bergapten as the

bergamot orange ''Citrus bergamia'', the bergamot orange (pronounced ), is a fragrant citrus fruit the size of an orange, with a yellow or green colour similar to a lime, depending on ripeness. Genetic research into the ancestral origins of extant citrus cul ...

whose essential oil is highly phototoxic. Indiscriminate use of

bergamot essential oil Bergamot essential oil is a cold-pressed essential oil produced by cells inside the rind of a bergamot orange fruit. It is a common flavouring and top note in perfumes. The scent of bergamot essential oil is similar to a sweet light orange pe ...

has led to several cases of

phytophotodermatitis Phytophotodermatitis, also known as berloque dermatitis,, margarita photodermatitis,, lime disease or lime phytodermatitis is a cutaneous phototoxic inflammatory reaction resulting from contact with a light-sensitizing botanical agent (such as ...

, a potentially severe skin inflammation. In these cases, the primary causal agent is believed to be bergapten. Cited i
CIR 2013
Cited i
CIR 2013

Hybrids

The

Key lime The Key lime or acid lime (''Citrus'' × ''aurantiifolia'' or ''C. aurantifolia'') is a citrus hybrid (''kaffir lime, C. hystrix'' × ''citron, C. medica'') native to tropical Southeast Asia. It has a spherical fruit, in diameter. The Key lime ...

(''Citrus aurantifolia'') is a hybrid of the micrantha and the

citron The citron (''Citrus medica''), historically cedrate, is a large fragrant citrus fruit with a thick Peel (fruit), rind. It is said to resemble a 'huge, rough lemon'. It is one of the Citrus taxonomy#Citrons, original citrus fruits from which al ...

. It, in turn, has been crossed with a

lemon The lemon (''Citrus'' × ''limon'') is a species of small evergreen tree in the ''Citrus'' genus of the flowering plant family Rutaceae. A true lemon is a hybrid of the citron and the bitter orange. Its origins are uncertain, but some ...

to produce the

Persian lime Persian lime (''Citrus'' × ''latifolia''), also known by other common names such as seedless lime, Bearss lime and Tahiti lime, is a citrus fruit species of hybrid origin, known only in cultivation. The Persian lime is a triploid cross betwe ...

(''C. latifolia''). There are lumias that are distinct micrantha/citron hybrids, such as the Pomme d'Adam, while other lumias, like the

Borneo Borneo () is the List of islands by area, third-largest island in the world, with an area of , and population of 23,053,723 (2020 national censuses). Situated at the geographic centre of Maritime Southeast Asia, it is one of the Greater Sunda ...

lemons, are micrantha/citron/pomelo tri-species hybrids. An Indonesian hybrid, the nansaran (''C. amblycarpa''), is a ''C. hystrix''/''C. reticulata'' cross.

References

External links

Searching for the Elusive Samuyao
"Our Philippine Trees" blog

"Our Philippine Trees" blog {{Taxonbar, from=Q20704151 Micrantha Flora of the Philippines Plants described in 1915