Cookia Sonn.; Fagarastrum G. Don.; Gallesioa M. Roem.; Myaris C. Presl; Quinaria Lour.; Piptostylis Dalzell; Polcyema Voigt (sec. Swingle and Reece 1967)
Clausena Burm. f. (sec. Swingle and Reece 1967, Bayer et al. 2009; sensu Tanaka sec. Cottin 2002)
Swingle and Reece (1967) noted on species problems in the genus:
"Of the twenty-three species of Clausena recognized here, ten were published from 1900 to 1930 and one as late as 1940. Of the others, one was published in 1892 and eleven from 1768 to 1875. It now appears that many of the older species, although they were described adequately enough to distinguish them from the other species known at the time, were nevertheless not described fully enough to separate them clearly from the many species recently discovered. Then, too, the range of the older species has been extended steadily as new botanical collections have been made. Very widely distributed species like C. excavata and C. anisata show, as might be expected, very many variations in their characters in specimens collected from widely different localities.
For these reasons a clear-cut definition of the species of Clausena will require a great amount of work which can be done only by using all the material in the leading herbaria of the world.
Tanaka, who assiduously studied Clausena (and also the other genera of Aurantioideae) from 1927 to 1937 in the herbaria of Europe, Asia, and America, has done much to clarify the species of this genus. He has published notes on them in all his valuable papers included in the series "Reviso aurantiacearum."
Swingle was permitted to borrow nearly a thousand sheets of material of Clausena from many of the leading herbaria of the Old World and the New, including all the Clausena material in the herbariums of the Royal Botanic Gardens at Kew and the Royal Botanic Garden at Calcutta. Thanks to these loans he was able to make a close study of many of the actual type specimens of the species of Clausena. In the study of this rich material he used a modification of Juel's method of softening herbarium material, after which it was fixed, dehydrated, imbedded, cut into serial microtome sections, double-stained, and finally mounted permanently on glass slides (Swingle 1939, p. 270).
In this work, Swingle had the skillful assistance of Dr. Albert H. Tillson. Figure 3-4, which shows longitudinal microtome sections of nine species of Clausena, makes clear how helpful this method is in studying herbarium material, especially the pistil just after the petals and stamens have fallen. It has not, however, been possible to work out all the species satisfactorily. Some species, like C. anisata, vary so greatly that months of work should be needed to study its numerous forms adequately, and other species are not well enough represented in herbaria for any complete study."
Crown compact or dense, not weeping. First-year twig surface pubescent; second- or third-year twig surface mottled; thorns absent or not persistent; prickles absent or not persistent. Petiole pubescent, length short or long, wings absent. Leaflets five to seven or greater than seven, margins entire, crenate/crenulate or bluntly toothed, rachis; wings absent, shade leaflet blades weakly conduplicate, sun leaflet blades weakly conduplicate. Scent of crushed leaflets somewhat to strongly malodorous. Fruit as broad as long or longer than broad; rind red or pink, green-yellow (6), yellow (7-10), or yellow-orange (11); rind texture smooth (1-3) or slightly rough (4-5); firmness membranous; navel absent; flesh red/purplish-tinged.
Swingle and Reece (1967) provided the following additional notes on the genus:
"Glycosmis and Clausena show very simple flower and fruit structures much like those found in some genera of other subfamilies of the family Rutaceae (such as Amyris in the subfamily Toddalioideae)."
"Trees or shrubs without spines; leaves odd-pinnate, leaflets alternate, usually 3-7 sometimes 19-32; rachis usually not winged; inflorescences terminal or axillary, paniculate or laxly racemose, flowers often in cymose clusters, flower buds small, subglobose or short-oval or oblong, never long-cylindric; flowers small, calyx 4-5 lobed; sepals fused into a cup below; petals free, 4 or 5 imbricate in the bud, usually elliptical; stamens 10, in 2 whorls, the outer row opposite, the sepals usually longer, filaments more or less dilated or flattened below, often geniculate where the filiform apical portion joins the flattened and expanded basal portion, anthers ovate or elliptical, rarely short and subglobose; gynophore well developed, usually a perfectly glabrous hourglass-shaped column resting on an annular nectary below and supporting (sometimes clasping) the base of the ovary above; ovary with 2-5 locules, often pubescent or glandular, ovules 2 in each locule (rarely 1); style deciduous, often shorter than the ovary or equaling it in length (rarely longer), thick, sometimes merging gradually into the ovary, often sharply delimited and narrowed where it joins the ovary, stigma inconspicuous, sometimes subcapitate after the style shrivels; fruits small, subglobose or ovate, with 2-5 segments, sometimes only 1 seed maturing; all flower parts usually showing many (not all) cells strongly impregnated with tannin residues.
The most distinctive morphological character of the genus Clausena is the gynophore, which in the typical species is a large, well-developed, hourglass-shaped structure supporting the ovary. It is perfectly glabrous and rests upon and merges into a short annular nectary below and sometimes expands above into a thin-lipped cup-like structure that encloses the base of the ovary. However, the gynophore varies greatly in the different groups of species and in some is so modified by expansions caused by development of oil glands that it is difficult to recognize. Nevertheless, it is present in all species of Clausena and separates them from the species of other related genera."
Swingle and Reece (1967) additionally provided the following notes on species relationships in the genus:
"The numerous species of this genus, still only imperfectly studied with respect to the minute flower characters, cannot be arranged now in natural sections or subgenera. It is clear to any taxonomist who looks over carefully a large collection of the species of Clausena that they can be classified into obviously related groups, some small, some large. Unfortunately, these groups are not clearly distinguished from one another but, on the contrary, seem rather to merge into allied groups without any sharp line of demarcation.
The study of the flower characters and in particular of the gynoecium by means of serial microtome sections has shown that important characters are found in the pistil that may help to define the natural groups of species.
The type species of the genus, C. excavata, has a striking hourglass-shaped gynophore which is completely glabrous. It arises from the annular nectary below and, after contracting, again expands and may even be slightly flaring where it joins the ovary, which is strongly hirsute. The ovary, which is 5-locular, merges into the style without any clear line of demarcation, and the style is not narrowed where it joins the tip of the ovary.
On the other hand, in C. indica the style is abruptly contracted and countersunk into a conical depression at the tip of the ovary, which has two to five locules. This species was made the type of the genus Piptostylis and belongs to a large group which includes many other species.
The species C. pentaphylla at present prevents a clear separation of the two groups outlined above. The pistil shows no sharp boundaries of gynophore, ovary, and style; the gynophore is as broad as the ovary—not hourglass-shaped—and is more or less lobed, often having short processes each ending in an oil gland. The style may be slightly contracted where it joins the top of the ovary but is frequently more or less swollen with oil glands just at this junction.
Clausena lansium stands apart from all the other species of the genus in having a star-shaped bud (due to its five strongly carinate petals) and a 5-angled ovary, corresponding in position to the five petal keels in a cross section of the bud. The pistil is unusually large; the ovary is very strongly hirsute and merges into the style, which is slightly contracted at the base. It is hourglass-shaped as in C. excavata. Furthermore, the twigs show a central gum canal, doubtless formed by a lysigenous breakdown of the tissues. The locules of the ovary contain scattered but well-developed hairs which arise on the dorsal and outer portion of the lateral walls and usually grow more or less toward the axis of the ovary. One much longer hair arises at the base of each locule and grows vertically upward, nearly to the top of the locular cavity (Penzig, 1887, p. 179, pl. 16, figs. 11, 12, 16). The fruits are apparently the largest in the genus and the locules of the ripe fruits are almost filled with a pulpy tissue which Penzig found to arise from the hypertrophy and multiplication of layers of cells nearest to the endocarp. This species was the type of the genus Cookia, but no other species having similar characters are yet known.
Clausena lenis also stands alone in the genus, having leathery petals and a most peculiar gynophore, no longer hourglass-shaped as in almost all the other species. Just above the thin annular nectary there is a narrow constriction followed by a cylindrical gynophore evidently swollen by a ring of 12 to 15 oil glands at its very base; it merges above into the ovary. The style is slender, two to three times as long as the ovary, by far the longest of any species in the genus, and contracted below, where it joins the ovary. The leaflets are subdentate, and the largest ones are lateral leaflets attached about two-thirds of the way up the rachis.
Clausena guillauminii has leaves showing dimorphic oil glands, the larger ones being 1/3 to 1/2 mm in diameter, and deep red by transmitted light; the flower parts show a single large oil gland at the tip of each sepal, each petal, each anther, and each locule of the ovary. C. wallichii has almost the same distribution of the oil glands in the flower parts. C. papuana shows great variation in the size of the oil glands in the leaflets and has the oil glands similarly distributed in the flower parts. These species may be closely related; certainly C. guillauminii, C. wallichii and C. luxurians are. The last-named species have the rachis slightly winged, unlike all other species of Clausena."
Swingle and Reece (1967) additionally noted that:
"The geographical distribution of Clausena is of interest since it has the widest range of any genus included in the orange subfamily, species being found all the way from northwestern India to China and Taiwan, south through the East Indian Archipelago to Timor, northern Australia, and New Guinea. Moreover, there is a group of three species that covers a wide range in Africa, from Ethiopia (Abyssinia) to Cape Province and through western Africa from Angola north to Sierra Leone.
There are wide differences in the character of the growth and the height of the species; they range all the way from shrubs 20 to 40 cm high in Indo-China to trees reaching a height of 20 m (66 feet) in Africa.
Several species of Clausena produce edible fruits, but up to now only one of them, the Chinese wampee, C. lansium, is cultivated (in southeastern China) on a commercial scale, with many varieties, the fruits varying greatly in size, flavor, and time of ripening. One other species, the Indian wampee, C. dentata var. dulcis , is gathered on a large scale from wild trees in the state of Madras in southern India, where it is a highly appreciated fruit, said by the British experts who have studied it to be of excellent flavor. At least two other forms are said to produce edible fruits, C. indica of India and Ceylon and C. dentata var. henryi of southwestern China.
The Chinese wampee, C. lansium, can be used as a rootstock for Citrus , provided a few twigs of the wampee are left growing below the graft. Other species of Clausena should be tested as stocks for Citrus and also for the edible-fruited species of Clausena.
Clausena anisum-olens , a species common in the Philippines from Luzon Island to Mindanao Island, grows in the forests from sea level to 1,500 m altitude. It is a small tree 3 to 6 m tall and has leaves with a strong odor of anis oil. West and Brown (1920, pp. 211-12) stated that the suggestion had been made that the leaves could be used locally in preparing anisado , a favorite alcoholic beverage among the Filipinos. The essential oil of the leaves was found by Brooks (1911, p. 344) to consist very largely (from 90 to 95 per cent) of methyl chavicol, which is easily converted into anethol, the true anis oil. The leaves yield about 1.2 per cent of oil after five hours’ distillation over steam. This essential oil is not known to occur in such a large proportion in any other plant of the family Rutaceae.
It is highly probable that other species of this large and very widely distributed genus, when studied carefully, will be found to be of value for their fruits, for use as rootstocks, for their essential oils, or for planting as ornamentals because of their abundant white flowers and handsome foliage."
For a recent revision of the genus, see Molino (1994: Revision du genre Clausena Burm. f.) in Bull. Mus. Natl. Hist. Nat., B, Adansonia 16: 105–153 (http://www.biodiversitylibrary.org/bibliography/13855).
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.
Brooks, B.T. 1911. New Philippine essential oils. Philippine Journal of Science, Sec. A, 6:333–353.
Cottin, R. 2002. Citrus of the World: A citrus directory. Version 2.0. France: SRA INRA-CIRAD.
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. 1939. New methods utilized in studying the taxonomy of the orange subfamily. Journal of the Washington Academy of Sciences 29:270.
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.
Tanaka, T. 1928. Revisio aurantiacearum, I. Bulletin de la Societe de Botanique de France 75: 708—15. (Reprinted in: Mem. Tanaka Citrus Exper. Sta. 1[21: 39–46 [1932].)
West, A.P. and W.H. Brown. 1920. Philippine resins, gums, seed-oils and essential oils. Philippines Bureau of Forestry Bulletin. 20: 224 pp.
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