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43. Lasianthus Jack, Trans. Linn. Soc. London. 14: 125. 1823.

粗叶木属 cu ye mu shu

Authors: Hua Zhu & Charlotte M. Taylor

Dasus Loureiro; Litosanthes Blume; Mephitidia Reinwardt ex Blume.

Erect subshrubs, shrubs, or rarely small trees, unarmed, with tissues sometimes fetid. Branches and branchlets terete, sometimes compressed, rarely fistulous; lenticels inconspicuous or conspicuous. Raphides present. Leaves opposite, distichous, usually thinly leathery or papery, base acute to rounded or cordate, apex acuminate, acute or cuspidate; midrib plane, depressed or slightly prominent adaxially, usually prominent abaxially; veins generally prominent abaxially, ascending at an angle of more than 45°, curved to margin or joining nerves above at margin; tertiary nervules parallel or reticulate; stipules caducous or usually persistent at least near stem apex, interpetiolar, well developed or reduced, triangular, lanceolate, ovate, or oblong, acute or obtuse. Inflorescence axillary, several flowered and glomerulate, capitate, cymose, or with flowers solitary, sessile or pedunculate, ebracteate or bracteate with bracts persistent or not, well developed, sometimes fused. Flowers bisexual, small, sessile or pedicellate. Calyx with hypanthium portion obovoid, ovoid, or campanulate; limb 3-6-dentate or lobed or rarely truncate. Corolla white, funnelform or salverform to urceolate (Lasianthus biflorus), from several millimeters long up to 2.5 cm, glabrous or hairy outside, inside glabrous or usually villous in throat; lobes 4-6, valvate or imbricate in bud. Stamens 4-6, inserted in corolla throat; filaments short; anthers linear or oblong, dorsifixed, included or exserted. Style linear; stigma lobes 3-9, linear or lanceolate, included or exserted. Ovary 3-9-celled, ovules 1 in each cell, basal, erect. Fruit blue or rarely white, black, or red, drupaceous, small, pulpy or fleshy, usually globose, smooth or warty, rounded or ridged, with calyx limb persistent; pyrenes 3-9 (sometimes fewer than that developing), thick walled, smooth, warty or sulcate on abaxial face, usually triangular in transverse section, with preformed germination slits; seed black, with abundant endosperm; embryo straight; cotyledon short, flattened; radicle long clavate.

About 184 species: 160 species in tropical Asia, ca. 20 in Africa, three in tropical America, and one in Australia; 33 species (seven endemic) in China.

Lasianthus is commonly collected in China. This genus has been studied in detail by H. Zhu for both China (Acta Phytotax. Sin. 32: 49-81. 1994; Syst. & Geogr. Pl. 72: 63-110. 2002; Acta Bot. Yunnan. 30: 308-314. 2008) and Thailand (Acta Phytotax. Sin. 39: 116-150. 2001: 53 species included). As Zhu detailed (loc. cit. 2002: 63), the characters that distinguish species of Lasianthus are mostly small and/or subtle, frequently ephemeral, and often difficult to see; and, consequently, the taxonomy of this genus is complicated. Lasianthus can be confused with some species of Damnacanthus, Diplospora, Prismatomeris, Saprosma, and Urophyllum, especially when collected only with young flower buds. Lasianthus (Chinese species) is rather distinctive vegetatively in its combination of leaf blades that are completely glabrous adaxially, petioles that are usually densely pubescent even when other parts of the plant are glabrescent or only sparsely pubescent, and small stipules that are usually persistent and also densely pubescent.

The leaf venation of Lasianthus frequently has a characteristic regular pattern, comprising subparallel or exceptionally regularly oriented tertiary veins ("nervules"). This is different, however, from the lineolate quaternary venation found in Antirhea, Timonius, and some other genera. A similar arrangement is found in some species of Urophyllum. Cai et al. (Acta Bot. Yunnan. 29: 497-512. 2007) studied leaf details of Lasianthus and [broadly] related genera, and Cai et al. (J. Syst. Evol. 46(1): 62-72. 2008) studied the pollen of a similar group.

The genus Litosanthes has been variously treated as a genus with one to several species, or included in Lasianthus. H. S. Lo (in FRPS 71(2): 106-108. 1999) treated Litosanthes as a separate genus of one or two species, as did Puff et al. (Rubiaceae of Thailand, 102. 2005). However, H. Zhu (loc. cit. 2002: 69) included it as a synonym of Lasianthus, as done here, based on morphological and molecular evidence.

Lasianthus verrucosus H. S. Lo (Bot. J. S. China 2: 2. 1993; type specimen: China. Hainan: Ledong, Q. Huang 820468, SCBI) was not seen. From H. S. Lo’s description and figure of this species, it has leaves with a looped venation, glabrous and fuscous when drying; inflorescence sessile or subsessile; calyx limb with 4 small, broadly triangular lobes; and pyrenes 4, verrucose on the abaxial face. Many Lasianthus specimens from Hainan were examined, but none was found matching the description of L. verrucosus. Consequently, this species is excluded from this account. From the original description it appears to be most similar to Saprosma merrillii and thus would likely key out as that species.

The phylogenetic relationships among species of Lasianthus and related genera were studied based on molecular data by Xiao and Zhu (Bot. Stud. (Taipei) 48: 227-232. 2007). Their results supported the inclusion of Litosanthes biflora and Saprosma crassipes within Lasianthus. Litosanthes is accordingly included here. However, S. crassipes has a 2-locular ovary and 2-pyrene drupes, which do not match the current circumscription of Lasianthus. Saprosma merrillii seems similar to S. crassipes, and their systematic position needs further study.

Lasianthus cyanocarpus Jack was reported from China by the Flora of Japan. However, true L. cyanocarpus has a restricted distribution in S Thailand and Malesia. This name is therefore misapplied in China and Japan, where the correct name for the species is L. hirsutus.

The following species was recorded from China but could not be treated here because no material was seen by the present authors: Lasianthus areolatus Dunn (J. Bot. 47: 376. 1909), recorded from Guangdong by Merrill and Chun (Sunyatsenia 1(1): 49. 1930).

1 Flowers in pedunculate congested cymes or subcapitate groups (though shortly pedunculate in L. chunii and sometimes subsessile in L. japonicus)   (2)
+ Flowers solitary or in sessile fascicles or glomerules (though sometimes pedunculate in L. henryi)   (8)
2 (1) Peduncles slender, 0.5-3 cm   (3)
+ Peduncles short, 0.1-0.4 cm, or if more than 0.6 cm then robust   (4)
3 (2) Leaves more than 3 cm; flowers 5-merous; pyrenes 5.   12 L. filipes
+ Leaves less than 3 cm; flowers 4-merous; pyrenes 2 or 4.   5 L. biflorus
4 (2) Peduncles very short, 1-2 mm   (5)
+ Peduncles conspicuous, 1.5-20 mm   (6)
5 (4) Branches and leaves abaxially appressed pubescent; leaves usually elliptic, acute or acuminate at apex, with nervules conspicuously elevated abaxially; fruit with 5 or 6 longitudinally elevated angles or ribs, strigillose.   10 L. chunii
+ Branches and leaves glabrous, or branches sparsely strigose when young and leaves abaxially strigose or hirtellous; leaves usually lanceolate, long caudate at apex, with nervules slightly prominent abaxially; fruit smooth, glabrous.   20 L. japonicus
6 (4) Bracts numerous, linear, 6-12 mm.   26 L. rhinocerotis
+ Bracts 2 and less than 1 cm, or reduced and apparently absent   (7)
7 (6) Branches depressed pubescent or subglabrous; peduncles relatively robust, 5-20 mm; bracts linear, 3-10 mm; calyx more than 5 mm with ovate-lanceolate lobes; corolla more than 1.5 cm.   4 L. biermannii
+ Branches sparsely puberulent to glabrous; peduncles slender, 1.5-5 mm; bracts 2 mm or shorter, usually inconspicuous; calyx less than 2.5 mm with triangular or subulate lobes; corolla 8.5 mm or shorter.   24 L. micranthus
8 (1) Bracts conspicuous   (9)
+ Bracts inconspicuous or absent   (16)
9 (8) Leaves slightly cordate to rounded and often oblique at base   (10)
+ Leaves cuneate or subrounded and not oblique at base   (11)
10 (9) Branches and leaves tomentose or setose; leaves 5-12 cm; stipules inconspicuous or to ca. 3 mm.   1 L. attenuatus
+ Branches and leaves glabrous, except very young branches subglabrous and leaves sparsely hairy on nerves abaxially; leaves 11-18 cm; stipules 5-6 mm.   27 L. rigidus
11 (9) Branches and leaves hirsute; bracts large, leaflike.   16 L. hirsutus
+ Branches and leaves glabrous or villous or appressed pubescent; bracts not leaflike   (12)
12 (11) Branches glabrous or thinly puberulent, leaves glabrous; bracts orbicular, leathery.   19 L. inodorus
+ Branches and leaves abaxially tomentose, villous, or densely appressed pubescent; bracts not orbicular, papery   (13)
13 (12) Leaves usually no more than 10 cm; bracts small, subulate; fruit with 4 pyrenes.   28 L. schmidtii
+ Leaves more than 12 cm; bracts ovate, lanceolate or linear; fruit with 5 or 6 pyrenes   (14)
14 (13) Stipules not conspicuous; bracts linear to lanceolate, up to 2 cm; fruit glabrous.   30 L. sikkimensis
+ Stipules triangular, up to 8 mm; outer bracts ovate and inner ones lanceolate, none more than 5 mm; fruit hairy   (15)
15 (14) Pubescence appressed on branches, leaves abaxially, stipules, bracts, and calyx, drupes subglabrous.   9 L. chrysoneurus
+ Tomentum dense and spreading on branches, leaves abaxially, stipules, bracts, calyx, and drupes.   25 L. obscurus
16 (8) Calyx lobes linear, longer than 5 mm   (17)
+ Calyx lobes not linear, no more than 5 mm   (18)
17 (16) Leaves 11-16 × 3.5-5.5 cm; lateral veins more than 10 pairs; branches and nerves abaxially densely yellow villous; calyx lobes equal in length and 9-14 mm.   7 L. chevalieri
+ Leaves 7-11 × 2.5-3 cm; lateral veins 5 or 6 pairs; branches and nerves abaxially hirsute; calyx lobes unequal in length, with longer ones up to 8 mm.   22 L. linearisepalus
18 (16) Calyx lobes longer than calyx tube or as long as tube   (19)
+ Calyx lobes clearly shorter than tube   (25)
19 (18) Leaves more than 12 cm   (20)
+ Leaves less than 12 cm   (21)
20 (19) Branches, leaf nerves abaxially, calyx, corolla, and fruit strigillose to glabrescent; calyx lobes linear-lanceolate.   6 L. calycinus
+ Branches, leaf nerves abaxially, and fruit tomentose with relatively long brown or fuscous hairs, calyx and corolla densely brown tomentose; calyx lobes oblong.   33 L. wardii
21 (19) Branches and leaf nerves abaxially glabrous or sparsely strigose; fruit glabrous.   23 L. lucidus
+ Branches and leaves abaxially very hairy; fruit pubescent   (22)
22 (21) Calyx limb divided nearly to base, lobes lanceolate or oblong and much longer than tube   (23)
+ Calyx limb not divided to base, lobes linear-lanceolate, slightly longer than or almost as long as tube   (24)
23 (22) Young branches and leaves abaxially appressed pubescent; calyx lobes oblong to elliptic or oblanceolate, obtuse at apex.   2 L. austrosinensis
+ Branches and leaves abaxially densely spreading villous; calyx lobes lanceolate, acuminate at apex.   11 L. curtisii
24 (22) Branches and leaves abaxially densely spreading villous.   14 L. formosensis
+ Branches and leaves abaxially densely appressed pubescent.   15 L. henryi
25 (18) Calyx lobes or teeth small, ovate and reflexed; leaves usually with more than 10 pairs of nerves, veinlets conspicuously reticulate.   8 L. chinensis
+ Calyx lobes or teeth not ovate and not reflexed; leaves usually with less than 10 pairs of nerves, veinlets parallel or subparallel or subreticulate   (26)
26 (25) Calyx cupulate, with limb truncate or minutely dentate; fruit crowned by enlarged calyx limb.   32 L. verticillatus
+ Calyx with conspicuous lobes; fruit crowned by persistent calyx lobes but these not enlarged   (27)
27 (26) Stipules triangular-lanceolate to linear-lanceolate, equal to or more than 3 mm, strigillose or hirsute; young branches strigillose or hirsute   (28)
+ Stipules triangular, less than 3 mm, puberulent; young branches puberulent or pubescent   (29)
28 (27) Stipules 3-5 mm; flowers 5-merous; fruit smooth, pyrenes 5.   29 L. simizui
+ Stipules usually more than 5 mm; flowers 4-merous; fruit verrucose, pyrenes 4.   31 L. trichophlebus
29 (27) Leaves more than 12 cm, lanceolate or oblong, lateral veins 6-9 pairs   (30)
+ Leaves less than 11 cm, ovate or ovate-oblong, lateral veins 4-6 pairs   (31)
30 (29) Leaves oblong, lateral veins 6-8 pairs, veinlets subparallel, conspicuously elevated abaxially; branches densely appressed pubescent, leaves abaxially at nerves and margins puberulent or ciliate.   18 L. hookeri
+ Leaves lanceolate to elliptic-lanceolate, lateral veins ca. 9 pairs, veinlets subreticulate with forks very slender; branches and leaf nerves abaxially sparsely appressed puberulent.   21 L. lancifolius
31 (29) Leaves 4-6 cm, less than 3 cm wide; branches and leaf nerves abaxially densely appressed hirsute.   3 L. austroyunnanensis
+ Leaves 6-10 cm, as narrow as 2 cm but usually more than 3 cm wide; branches and leaf nerves abaxially glabrous or pubescent or villous   (32)
32 (31) Branches and leaf nerves abaxially glabrous or sparsely appressed pubescent; calyx sparsely pubescent, with 5 triangular teeth; fruit glabrous.   13 L. fordii
+ Branches and leaves abaxially densely villous; calyx densely strigillose, with 5 minute and broadly triangular teeth; fruit strigillose.   17 L. hispidulus

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