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Citrus ID

 

Australian Finger

 

Synonyms

 

Finger, Queensland Finger, Queensland Native (sec. Cottin 2002); Citrus australasica F. Muell. (sec. Swingle and Reece 1967)

Cultivar or taxon

 

Citrus australasica F. Muell. (sensu Mabberley 2004, Bayer et al. 2009); Microcitrus australasica (F. Muell.) Swingle (sensu Swingle and Reece 1967; sensu Tanaka sec. Cottin 2002)

Origin

 

The Chiefland Budwood Facility (2010) provided the following notes on the cultivar (clone DPI-205-1): "Received from Dr. Prevatt, Florida Southern College in 1977, originally from Australia."

Description

 

Crown compact or dense, not weeping. First-year twig surface glabrous; second- or third-year twig surface striate; thorns straight; prickles absent or not persistent. Petiole glabrous, length short, wings narrow and adjoining the blade. Leaflets one, margins bluntly toothed, shade leaflet blades flat, sun leaflet blades weakly conduplicate. Scent of crushed leaflets sweetly orange-like. Fruit as broad as long or longer than broad; rind black, red, pink, dark green (3), medium green (4), green-yellow (6), yellow (7-10), or yellow-orange (11); rind texture slightly rough (4-5); firmness leathery; navel absent; flesh green/greenish.

Swingle and Reece (1967) provided the following additional notes on the species:

"First leaves of young seedlings small, 3-5 X 2-4 mm, ovate, with very short wingless petioles borne on numerous slender, horizontal twigs with internodes often only 2-4 mm long, with sharp, slender spines, 7-12 mm long, at the nodes; the upright twigs of young plants have similar leaves and spines but the internodes are sometimes 5-8 mm long; the upright, strongly angled, vigorous twigs of mature trees, which have internodes 8-12 mm long with single sharp spines, 5-10 mm long, have lozenge-shaped leaves, 22-25 X 14-15 mm, obscurely toothed in the upper half, gradually narrowed to a blunt, truncate base with which the petiole articulates; lateral veins faintly marked above, more clearly below, 6-10 pairs, arising at an angle of 35°-45° with the midrib, lower ones longer, upper ones soon branching, all with several anastomosing curved cross-veins; leaves tapering into a truncate or emarginate tip, those on lateral twigs 8-20 X 2-10 mm, the smaller ones abruptly truncate, often irregularly emarginate; spines slender, short, 3-8 mm long; flowers arising singly in the axils of the leaves (or occasionally in pairs); flower buds subglobose or obovate, 4 X 5 mm, borne on very short pedicels, 1-2 mm long; flowers usually 5-merous but sometimes 3-4-merous; sepals free, small, concave, minutely ciliate; petals oblong, 7-8 mm long; stamens 20-25, free, pistils short, stout, ovary with 5-7 locules; ovules numerous, 8-16 (or even 20) in each locule; fruits cylindric-fusiform, 6.5-10 X 1.5-2.5 cm, often slightly curved, narrowed at both tip and base, often showing a blunt protuberance at one or both ends; peel rough with numerous oil glands, greenish-yellow at maturity; pulp-vesicles nearly free or loosely cohering, long-stalked, ovoid, ending in a very blunt or rounded tip, about 1.7-3 X 1.2-1.5 mm, borne on a slender stalk 1-2 mm long; seeds numerous, small, 6-7 mm long, ovoid, monoembryonic, usually flattened on one side and often showing small, shallow depressions on the other faces (probably caused by mutual pressure of the pulp-vesicles exerted during development of the fruit); testa smooth (not wrinkled as in Eremocitrus glauca); cotyledons hypogeous in germination.

This, the type species of the genus Microcitrus, has several characters separating it from all of the species of Citrus. It is also very clearly separated from the other species of Microcitrus by its very long, slender fruits that are unique in the orange subfamily (see fig. 3-44,E ). They have numerous seeds (or rudiments) in each segment (more numerous than in any other true citrus fruit). The pulp is composed of loosely grouped, long-stalked, subglobose or pyriform pulp-vesicles, tapering bluntly to the tip. These pulp-vesicles are very different from those of M. australis but are much like those of M. inodora; they also resemble somewhat those of Citrus (Papeda) hystrix, as noted by Penzig (1887, pp. 214-17), who was the first to describe the anatomy of the fruits, seeds, and pulp-vesicles of M. australasica. The very acrid pulp has a harsh aftertaste, probably due to droplets of acrid oil in the pulp-vesicles, such as have been found in the Australian round lime. Francis (1929, p. 174) stated that the fruits, both of this species and of M. australis, "have a lemon-like flavor accompanied by a taste of a turpentine nature."

The finger-lime of the coastal regions of northeastern Australia is a tall shrub or small tree and makes a handsome ornamental. The seedlings are very spiny. The first leaves are minute linear cataphylls; these gradually merge into juvenile foliage which, in turn, merges into the mature foliage, the leaves of which are smaller than those of any other True Citrus Fruit Tree with the exception of Eremocitrus glauca when the latter occurs in very dry situations. The branches on young plants often stand out nearly at right angles to the stem, giving the young plant the appearance of a very dwarfed fir tree. This species is precocious; Oliver (1911, p. 15) figured a small branch of a two-year-old seedling bearing two fruits.

Uphof (1932, pp. 138-39), in an examination of five trees of M. australasica, found that most of the flowers were male and that only a very few were perfect. He examined the flowers on eight twigs and found, out of 161 flowers, that 151 were male and that only ten were perfect."

The Chiefland Budwood Facility (2010) provided the following additional notes on the cultivar (clone DPI-205-1): "Very long slender fruit, numerous seeds, pyriform pulp vesicles, small, crenate leaves, acid, aftertaste, very thorny, small leaves."

Notes

 

The Chiefland Budwood Facility (2010) provided the following notes on the cultivar (clone DPI-205-1): "From Wikipedia: The finger lime has been recently popularized as a gourmet bushfood. The globular Juice vesicles have been likened to a "caviar lime", which can be used as a garnish or added to various recipes. The fresh vesicles have the effect of a burst of effervescent tangy flavor as they are chewed. The fruit juice is acidic and similar to that of a lime. Marmalade and pickles are also made from finger lime. The finger lime peel can be dried and used as a flavoring spice."

References

 

Bayer, R.J., D.J. Mabberley, C. Morton, C.H. Miller, I.K. Sharma, B.E. Pfeil, S. Rich, R. Hitchcock, and S. Sykes. 2009. A molecular phylogeny of the orange subfamily (Rutaceae: Aurantioideae) using nine cpDNA sequences. American Journal of Botany 96: 668–685.

Chiefland Budwood Facility. 2010. 2010 Annual report July 1, 2009 - June 30, 2010. Bureau of Citrus Budwood Registration, Florida Department of Agriculture & Consumer Services, Winter Haven.

Cottin, R. 2002. Citrus of the World: A citrus directory. Version 2.0. France: SRA INRA-CIRAD.

Francis, W.D. 1929. Australian rain-forest trees excluding the species confined to the tropics. Comming, Gov't. Printer, Brisbane. 347 pp.

Mabberley, D.J. 2004. Citrus (Rutaceae): A review of recent advances in etymology, systematics and medical applications. Blumea 49: 481–498.

Oliver, G.W. 1911. The seeding inarch and nurse-plant methods of propagation. U.S. Department of Agriculture Bureau of Plant Industry Bullletin 202. 43 pp.

Penzig, O. 1887. Studi botanici sugli agrumi e sulle piante affini. Tip. Eredi Botta, Rome. Ministero di Agricoltura, Industria e Comercio. Annali di Agricoltura, No. 116. 596 pp. and atlas of 58 pls.

Swingle, W.T. and P.C. Reece. 1967. The botany of Citrus and its wild relatives. In: Reuther, W., H.J. Webber, and L.D. Batchelor (eds.). The Citrus industry. Ed. 2. Vol. I. University of California, Riverside. http://lib.ucr.edu/agnic/webber/Vol1/Chapter3.html.

Uphof, J.C.T. 1932. Wissenschaftliche Beobachtungen and [sic] Versuche an Agrumen. IV. Der polygamische Zustand einiger Citrusarten. Gartenbauwissenschaft 7: 121–141.

Resources

 

Search for this cultivar in NCBI Entrez or NCBI Nucleotide

 

Citrus ID Edition 2
October, 2011
idtools.org