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7. Lauraceae

樟科 zhang ke

Authors: Shugang Li, Xi-wen Li, Jie Li, Puhua Huang, Fa-Nan Wei, Hongbin Cui & Henk van der Werff

Trees or shrubs (Cassytha a twining parasitic perennial herb with leaves reduced or absent), mostly evergreen (deciduous in temperate regions), sometimes dioecious. Bark and foliage usually aromatic. Leaves usually alternate, occasionally opposite or subopposite or verticillate, simple, usually entire, rarely lobed (Sassafras), mostly pinninerved and subpalmately veined, or often triplinerved, usually punctate and leathery, estipulate. Flowers in usually axillary, occasionally subterminal, panicles, spikes, racemes, or pseudoumbels, generally bisexual, sometimes unisexual, actinomorphic, mostly 3-merous, also 2-merous, small, greenish, yellowish, or white. Perianth biseriate, of usually 4 or 6 basally connate usually undifferentiated sepal-like segments, deciduous or persistent; perianth tube usually persisting as a cupule at base of fruit. Androecium typically of 4 whorls of 3 stamens each, adnate to perianth tube, innermost whorl rarely united, usually reduced to staminodes; filaments usually free, 3rd whorl usually bearing 2 usually sessile and distinct basal glandular protuberances; anthers basifixed, 2-celled or 4-celled at anthesis, those of 2 outer whorls mostly introrse, inner 3rd whorl extrorse, dehiscing by flaplike valves opening upward. Pistil 1; ovary usually superior, 1-loculed; ovule solitary, anatropous, pendulous, placentation parietal; style 1; stigma 1, occasionally 2- or 3-lobed. Fruit a drupe or berry usually surrounded at base by enlarged and often persistent perianth tube seated on a large receptacle or pedicel. Seed with large straight embryo; endosperm absent.

About 45 genera and 2000-2500 species: tropical and subtropical regions but mostly in tropical SE Asia and tropical America; 25 genera (two endemic, two introduced) and 445 species (316 endemic, three introduced) in China; two additional species (one endemic) are of uncertain placement.

The Lauraceae are economically important as sources of medicine, timber, nutritious fruits (e.g., Persea americana), spices (e.g., Cinnamomum cassia, C. subavenium, Laurus nobilis), and perfumes. The fruits of Actinodaphne, Cinnamomum, Cryptocarya, Lindera, Litsea, and Syndiclis contain abundant oil and fat. Cinnamomum trees, such as Cinnamomum camphora, C. glanduliferum, and C. parthenoxylon, yield camphor and essential oil, which are used for making perfumes and medicines. The bark of C. cassia and the roots of Lindera aggregata are famous traditional Chinese medicines.

The Chinese species of Lauraceae remain poorly known and difficult to identify. The main reason for this is that for a substantial number of species the fruits or flowers are not known. This makes generic placement of such species uncertain, since most genera are defined by floral characters. A second problem is that characters of both flowers and fruits are used in most generic keys and since specimens almost never bear both flowers and fruits, identification is often almost impossible. A drastic remedy for this problem would be to make keys based on flowering specimens and list species known only with fruits as incompletely known species and not include them in the keys. This approach has not been followed in this treatment.

The genera are here maintained as they have been recognized in earlier works on Chinese Lauraceae. The present authors are aware that this will seem inconsistent; for instance, in the case of Sassafras, species with 2-celled and 4-celled anthers are included in the same genus, while in other cases pairs of genera are separated based on this character (for example Lindera-Litsea, Alseodaphne-Nothaphoebe, and Parasassafras-Sinosassafras). Generic boundaries in the Litsea group (Actinodaphne, Dodecadenia, Iteadaphne, Lindera, Litsea, Neolitsea, Parasassafras, and Sinosassafras) are not well defined, and generic concepts are likely to change after further research.

Aside from these problems, there are a number of vegetative characters that are helpful in the identification process. They are listed below.

Leaves opposite or subopposite: Beilschmiedia p.p., Caryodaphnopsis, Cinnamomum p.p.

Leaves verticillate or clustered: Actinodaphne, Neolitsea; rarely in Lindera (L. megaphylla) and Litsea (L. verticillata); weakly clustered in Alseodaphne, Dehaasia, Machilus, Phoebe.

Leaves triplinerved and alternate: Cinnamomum p.p., Cryptocarya p.p., Lindera p.p., Neocinnamomum.

Leaves triplinerved and clustered: Neolitsea.

Leaves triplinerved and opposite: Caryodaphnopsis, Cinnamomum p.p.

Leaves lobed: Lindera p.p., Sassafras.

Leaves with tufts of hairs in axils of lateral veins: Cinnamomum p.p.

The three genera Machilus, Persea, and Phoebe cannot be identified adequately by floral characters; they have been separated traditionally on the fruit characters listed in the key.

Li Hsi-wen et al. 1982. Lauraceae. In: Li Hsi-wen, ed., Fl. Reipubl. Popularis Sin. 31: 1-463.

One of the present authors (van der Werff) provides this alternative key to genera. Nothaphoebe is deliberately not included; see the comment under that genus (p. 200).


Key to genera

1 Twining parasitic vines.   25 Cassytha
+ Leafy trees or shrubs   (2)
       
2 (1) Flowers unisexual, rarely bisexual, in pseudoumbels or racemes, rarely solitary; bracts large, forming an involucre   (3)
+ Flowers bisexual, rarely unisexual, in panicles or clusters, rarely in pseudoumbels; bracts small, not forming an involucre   (10)
       
3 (2) Flowers 2-merous; perianth lobes 4   (4)
+ Flowers 3-merous; perianth lobes 6   (5)
       
4 (3) Male flowers: 12 stamens in 3 whorls, all stamens or those of 2nd and 3rd whorl glandular, anthers 2-celled; female flowers: staminodes 4.   1 Laurus
+ Male flowers: 6 stamens in 3 whorls, only those of 3rd whorl glandular, anthers 4-celled; female flowers: staminodes 6.   2 Neolitsea
       
5 (3) Bracts of involucre imbricate, caducous or late deciduous   (6)
+ Bracts of involucre decussate, persistent or late deciduous   (7)
       
6 (5) Deciduous habit; leaves alternate, unlobed or 2- or 3-lobed; inflorescence of racemes.   7 Sassafras
+ Evergreen habit; leaves usually whorled, rarely opposite or alternate, unlobed; inflorescence of umbels.   8 Actinodaphne
       
7 (5) Anthers 4-celled   (8)
+ Anthers 2-celled   (9)
       
8 (7) Inflorescence many flowered.   3 Litsea
+ Inflorescence 1-flowered.   4 Dodecadenia
       
9 (7) Flowers functionally unisexual; umbel mostly many flowered.   5 Lindera
+ Flowers unisexual or polygamous; pseudoumbel 1-flowered.   6 Iteadaphne
       
10 (2) Anthers (1 or)2-celled   (11)
+ Anthers 4-celled   (16)
       
11 (10) Fruit enveloped by dilated perianth tube.   24 Cryptocarya
+ Fruit not enveloped by perianth tube   (12)
       
12 (11) Flowers 2-merous; perianth lobes 4; fertile stamens 4.   23 Syndiclis
+ Flowers 3-merous; perianth lobes 6; fertile stamens 3 or 9   (13)
       
13 (12) Flowers functionally unisexual, in pseudoumbels.   19 Sinosassafras
+ Flowers bisexual, in panicles   (14)
       
14 (13) Fertile stamens 3.   20 Endiandra
+ Fertile stamens 6 or 9   (15)
       
15 (14) Tepals longer than stamens; stamens included in flower; anther cells laterally opening, slit-like.   21 Beilschmiedia
+ Tepals shorter than stamens; stamens exserted from flower; anther cells apically opening, small, roundish.   22 Sinopora
       
16 (10) Perianth tube forming a perianth cup when in fruit   (17)
+ Perianth tube not forming a perianth cup when in fruit   (19)
       
17 (16) Flowers in umbels.   9 Parasassafras
+ Flowers in panicles or glomerules   (18)
       
18 (17) Flowers in panicles; anther cells in pairs above each other; perianth lobes deciduous or persistent but not thickened when in fruit; leaves alternate or subopposite, pinninerved, trinerved, or triplinerved.   10 Cinnamomum
+ Flowers in glomerules; anther cells in an arc or in pairs above each other, lower 2 cells large and lateral; perianth lobes persistent and dilated when in fruit; leaves alternate, triplinerved.   11 Neocinnamomum
       
19 (16) Perianth lobes persistent when in fruit   (20)
+ Perianth lobes deciduous when in fruit   (22)
       
20 (19) Persistent perianth lobes soft, longer, reflexed or patent, not tightly clasped at fruit base.   14 Machilus
+ Persistent perianth lobes durable, shorter, erect or patent, tightly clasped at fruit base   (21)
       
21 (20) Perianth lobes equal in size, sometimes outer 3 somewhat smaller; filaments long.   12 Phoebe
+ Perianth lobes unequal in size, outer 3 conspicuously smaller; filaments very short.   13 Nothaphoebe
       
22 (19) Fruit stalk dilated, fleshy, always colored; anthers 2-celled.   15 Dehaasia
+ Fruit stalk barely or not dilated; if fruit stalk dilated, anthers 4-celled   (23)
       
23 (22) Leaves opposite, trinerved or triplinerved; perianth lobes unequal in size, outer 3 smaller.   16 Caryodaphnopsis
+ Leaves alternate, pinninerved; perianth lobes equal or subequal in size   (24)
       
24 (23) Perianth large; fruit fleshy, large-sized; plants cultivated.   17 Persea
+ Perianth small- or medium-sized; fruit somewhat fleshy, small- to medium-sized; plants native.   18 Alseodaphne

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