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(Last Modified On 3/18/2013)
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(Last Modified On 3/18/2013)
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Genus
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Croton L.
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PlaceOfPublication
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Sp. P1. 1004, 1753
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Reference
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Gen. P1. ed. 5, 436, 1754.
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Description
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Trees, shrubs, or herbs; monoecious or dioecious; stems usually with colored sap, the indumentum (at least in part) stellate or lepidote. Leaves alternate; petiolate (petioles often with glands near the top); stipulate (stipules sometimes obscure or obsolete); blades pinnately or palmately veined, sometimes lobed, entire or serrate. Inflorescences spicate-racemose (or sometimes paniculate or subcapitate), terminal or axillary; bisexual racemes mostly with 9 flowers solitary at proximal nodes, male 1-several at distal nodes (sometimes at same nodes with female). Staminate flowers with 4-6 imbricate or (most often) valvate calyx-lobes; disc entire or dis- sected; petals usually 5 (rarely absent); stamens mostly 8-50, free, the filaments inflexed in bud; pollen grains globose, inaperturate, clavate; pistillode absent. Pistillate flowers with 4-10 (mostly 5-7) imbricate or valvate calyx-lobes; disc usually entire, rarely dissected, sometimes with staminodia; petals 5, often reduced or absent; ovary of 3 (rarely 2) carpels, the ovules 1 per locule; the styles more or less free, once to repeatedly bifid or bipartite. Fruits capsular; seeds terete to compressed, dry, carunculate, endosperm present, the embryo with broad cotyledons.
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Habit
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Trees, shrubs, or herbs
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Distribution
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Nearly 1000 species have been described in this natural but polymorphic genus. The majority of the species are American, but most of these occur in South America and the West Indies; about 80 distinct species have been recognized in continental North America.
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Note
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Although Croton is relatively poorly represented in Panama, with only 13 species, these belong to 6 different sections which include most of the important neotropical groups within the genus. A very high percentage of the Panamanian specimens of Crotoin have been misidentified in the past, partly due to the obscure treatments in the literature and partly to some necessary nomenclatural changes. None of the species proposed from Panama since the original treatments by Klotzsch and Mueller can be maintained, and it does not appear that there are any endemic Panamanian species of Croton, except perhaps C. billbergianus. Much of the difficulty in the genus appears to be the result of a misconception by previous workers that American species of Croton tend to be narrowly restricted in range. The experience gained during the preparation of this treatment shows that this does not accord with the facts; several common woody Panamanian species (e.g. C. schiedeanus, C. pungens and C. hircinus) range far beyond our boundaries into South America. A few species, C. panamensis especially, are quite variable and cannot be definitively treated in a local revision such as this. Finally, it must be admitted that the species in sect. Eluteria pose the greatest number of problems, since these taxa are similar to various extra-Panamanian ones, and both flowers and seeds are necessary to establish specific identities. These lepidote taxa of Croton need careful field study in Panama and adjacent regions before the treat- ment proposed here can be accepted as authoritative.
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Key
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a. Staminate flowers petaliferous; leaves stipulate; indumentum various. b. Indumentum lepidote; petals in 9 flower reduced, similar to the A; leaves with deciduous stipules and eglandular petioles; inflorescences strictly axillary. (sect. Eluterid) c. Stamens 9-12, filaments glabrous; anthers 0.6-0.8 mm long; petals of 8 flower not lepidote or with only 1 or 2 scales; seeds mostly 7 mm long or less. d. Leaves more or less oblong-elliptic, pinnately veined; inflorescences mostly 2 cm long or more; pedicel of 9 flower mostly 10 mm long or more -------------------------1. C. schiedeanus dd. Leaves ovate, ? cordate and (3-)5-veined at base; inflorescences 1 cm long or less; pedicel of 9 flower only 1-2 mm long . 2. C. pseudoniveus cc. Stamens 14-17 or if fewer then filaments hirsutulous; anthers 1-1.2 mm long; petals of 8 flower lepidote; seeds 15 mm long or more. e. Stamens (10-)11-13, filaments hirsutulous; leaves pinnately veined 9 flowers mostly 3 or 4 per raceme; seeds 20-22 mm long .. .----- .--------------------------------------------- 3. C . tenuicaudatus ee. Stamens 15, filaments glabrous; leaves 3-5 veined at base; 9 flowers mostly 1 or 2 per raceme; seeds 15-18 mm long ... . 4. C. pyriticus bb. Indumentum not lepidote, the trichomes mostly or entirely stellate or dendritic; petals in 9 flower distinctly reduced or absent [sometimes fairly well developed in C. panamensis]; petioles with distinct glands at junction with blade [except in C. hircinus]; inflorescences terminal (at least in part). f. Leaves unlobed (with obscure and rudimentary indications of lobing in C. hircinus); 8 calyx-lobes usually distinctly valvate in the bud; receptacle of 8 flower usually villose; seeds not tetragonal; habAt various. g. Lower c-ymules of inflorescence with both 8 and 9 flowers at the same nodes, styles bifid or bipartite. (sect. Cyclostigma) h. Pistillate flowers distinctly pedicellate (pedicels mostly 3-6 mm long; inflorescences mostly 2-4 dm long; stamens 13-20; petals of 8 flowers with villose margins; styles glabrous or nearly so, seeds less than 5 mm long -.--------------------------5. C. panamensis hh. Pistillate flowers subsessile (pedicels becoming at most 2 mm long); inflorescences mostly 1-2 dm long; stamens 27-43; petals of 8 flowers glabrous, margins minutely ciliate; styles distinctly stellate pubescent; seeds at least 5 mm long - 6. C. pungens gg. Lower nodes of bisexual inflorescences with only 9 flowers. j. Styles twice to four times bifid; shrubs or trees (sect. Croton) k. Pistillate calyx-lobes not prominently glandular- toothed; stamens 14-16; petioles with distinct apical glands. 1. Pistillate calyx-lobes elliptic to oblong, not accrescent, less than 5 mm broad; petals of 3 flower not over 4 mm long; leaves 7-9- veined at base, entire, with petioles mostly 5-20 cm long ------------------------7. C. billbergianus 11. Pistillate calyx-lobes ovate, reduplicate-valvate, accrescent, becoming 7-8 mm long and broad; petals of 8 flower 4.5-5 mm long; leaves mostly 5 veined at base, entire to denticulate, with petioles 1-3.5 cm long -8. C. fragrans kk. Pistillate calyx-lobes coarsely glandular-toothed below; stamens 10-12; petiolar glands obscure or obsolete - 9. C. hircinus jj. Styles once bifid; annual herbs. (sect. Geiseleria) m. Leaves coarsely and sharply serrate (major teeth usually not over 10 per side); stamens 8-10; styles less than 1.5 mm long, + spreading ------------------------------------------10. C . trinitatis mm. Leaves more finely and/or bluntly toothed; stamens 11; styles more than 1.5 mm long, more or less erect. n. Stems coarsely hispid; leaves mostly ovate, pointed at the tip, petiolar glands stalked; bracts with long gland-tipped processes; seeds 2.6-3.1 mm long - 11. C. hirtus nn. Stems not coarsely hispid; leaves mostly elliptic or oblong, blunt at the tip, petiolar glands sessile; bracts eglandular; seeds 2.8- 3.5 mm long ------- [C. glandulosus] ff. Leaf-blades deeply 3-5-lobed; 8 calyx-lobes distinctly imbricate in bud; receptacle of 8 flower glabrous; seeds tetragonal; annual herb. (sect. Astraea) -------------------------------------------------------------12. C. lobatus aa. Flowers apetalous; stipules and petiolar glands absent; leaves with stellate- lepidote indumentum above, lepidote beneath; stamens 10-12, filaments hir- sutulous; styles 3 times bifid; seeds deciduously stellate, ca 5 mm long. (sect. Drepadenium) .................. 13. C. punctatus
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