Cannabaceae Martinov

Torres, R.B. (2011). Neotropical Cannabaceae.

Morphology

Description

Trees or shrubs, sometimes climbing, sometimes armed, monoecious , dioecious or polygamous. Leaves alternate , usually distichous , rarely opposite, deciduous or persistent , simple , margin entire to serrate , venation pinnate , usually trinerved , cystoliths present, stipules lateral . Inflorescence axillary , racemose, fasciculate or rarely reduced to only one flower . Flowers unisexual (rarely bisexual ), not showy, usually 4-5 tepals, free or connate ; stamens 4-5, opposite the tepals, anthers longitudinally dehiscent ; ovary superior , 2-carpels, 1-locular, locule 1-ovulate, placentation pendulous. Fruit drupaceous ; seeds rounded , embryo curved.

General Description

Notes on delimitation

• Celtis, Trema and other taxa of woody Cannabaceae were formerly placed in Ulmaceae, subfamily Celtidoideae or Celtidaceae. Although some species of Aphananthe have secondary veins of leaves ending in the teeth, as in the Ulmaceae, it is considered that this feature evolved independently from that of Ulmaceae.
• The presence of unisexual flowers in Cannabaceae is an important feature for the separation from Ulmaceae. However, Trema micrantha has rare bisexual flowers, which are protogynous and sometimes functionally male.

Number of genera

About 9 genera, with 4 genera and 20 species in the Neotropics:

• Aphananthe - A. monoica (Hemsl.) J.-F. Leroy.
• Celtis - C. australis L.; C. berteroana Urb.; C. brasiliensis (Gardner) Planch.; C. caudata Planch.; C. chichape (Wedd.) Miq.; C. ehrenbergiana (Klotzsch) Liebm.; C. fluminensis Carauta; C. iguanaea (Jacq.) Sarg.; C. loxensis C.C. Berg; C. pubescens (Kunth) Spreng.; C. reticulata Torr.; C. schippii Standl.; C. spinosa Spreng.; C. tala Gillies ex Planch.; C. trinervia Lam.
• Lozanella - L. enantiophylla (Donn. Sm.) Killip & C.V. Morton; L. permollis Killip & C.V. Morton.
• Trema - T. micrantha (L.) Blume; T. integerrima (Beurl.) Standl.

General notes

• The Celtis species are hard to identify because their flowers are very similar and the morphological characters usually cited by different authors have great variation. The taxonomy of the genus requires extensive revision, because the available studies do not adequately account for the status of the many published names.
• Trema micrantha is a species of wide geographical distribution and great morphological variability. Studies on its biology in two natural populations revealed that several plants do change their sex during the breeding season. These studies revealed also the occurrence of rare bisexual flowers. We accept two species for the Neotropical region but the genus, like Celtis, also needs extensive revision.
• Some species of Celtis provide hardwood, some are ornamental or have edible fruits. The fruits of Aphananthemonoica are also edible. Trema micrantha is an important species in the regeneration of deforested areas; its fruits are enjoyed by birds; the bark can be used to make handmade paper and its timber for manufacturing industrial paper.

Status

• Lozanella endemic.  Alphananthe, Celtis and Trema occur in other regions and continents.

Distribution

Distribution in the Neotropics

• Aphananthe Planch. - Mexico, Guatemala, El Salvador, Honduras and Nicaragua.
• Celtis L. - Mexico, Central America and Caribbean islands to Argentina.
• Lozanella Greenm. - Mexico to Bolivia.
• Trema Lour. - Mexico, Central America and Caribbean islands to Argentina

Diagnostic

Other important characters

• Trees or scandent shrubs with spines (Celtis).
• Lozanella is very similar to Trema, but with opposite leaves and fused stipules.

Distinguishing characters (always present)

• Trees, or shrubs, sometimes scandent, leaves simple, alternate, generally distichous, rarely opposite (Lozanella), with stipules, cystoliths present; flowers unisexual, inconspicuous; fruit a drupe.

Key differences from similar families

• Plants without latex, sometimes armed, never urticating (latex in all parenchymatic tissues in Moraceae or restricted to bark in Urticaceae; plants unarmed in Ulmaceae, Moraceae (except Maclura) and Urticaceae; sometimes urticating in Urticaceae).
• Leaves simple, alternate, distichous, rarely opposite (leaves simple or lobed, alternate, distichous, spiral or opposite in Moraceae and Urticaceae).
• Leaves usually 3-nervate from base (penninerved with secondary venation ending in the teeth of the margin in Ulmaceae; penninerved or palmate in Moraceae and Urticaceae).
• Flower unisexual with apical placentation (flower unisexual or bisexual in Ulmaceae; basal placentation in Urticaceae).
• Fruitdrupaceous (samara or nut in Ulmaceae; drupe or achene in Moraceae and Urticaceae, sometimes forming a compoundfruit).

Useful tips for generic identification

Key to genera of Neotropical Cannabaceae

1. Leaves opposite; stipules united, leaving a conspicuous interpetiolar scar .... Lozanella
1. Leaves alternate; stipules free or united only at their base .... 2
2. Monoecious plants, leaves pinnately veined, the secondary veins ending at the margin .... Aphananthe
2. Monoecious, dioecious or polygamous plants, leaves pinnately veined, usually 3-nerved at base, the secondary veins ending before the margin .... 3
3. Trees, unarmed; tepals induplicate-valvate in bud, stigmas 2, simple.... Trema
3. Trees or shrubs, sometimes scandent, sometimes armed; tepals imbricate in bud, stigmas 2, simple or bifurcate .... Celtis

Literature

Important literature

Berg, C.C. & Dahlberg, S.V. 2001. A revision of Celtis subg. Mertensia (Ulmaceae). Brittonia 53(1): 66-81.

Killip, E.P. & Morton, C.V. 1931. The genus Lozanella. Journal of the Washington Academy of Sciences21: 336-339.

Miller, J.S. & Berry, P.E. 2005. Ulmaceae. In: P.E. Berry, K. Yatskievych & B.K. Holst (eds.), Flora of the Venezuelan Guayana, pp. 386-390. The Missouri Botanical Garden, St. Louis.

Nee, M. 1984. Ulmaceae. In: Flora de Vera Cruz, Fascículo 40, pp. 34-38. Instituto Nacional de Investigaciones sobre Recursos Bióticos, Vera Cruz.

Pennington, T.D., Reynel, C. & Daza, A. 2004. Illustrated guide to the trees of Peru. pp. 93-96.  David Hunt, Sherborne.

Systma, K.J.; Morawetz, J., Pires, J.C., Nepokroef, M., Conti, E., Zjhra, M., Hall, J.C. & Chase, M.W. 2002. Urticalean Rosids: circumscription, Rosid ancestry, and phylogenetics based on rbcL, trnL-F, and ndhF sequences. American Journal of Botany 89(9): 1531-1546.

Romanczuk, M.C. & Martinez, MA.P. 1978. Las especies del género Celtis (Ulmaceae) en la flora Argentina. Darwiniana 21(2-4): 541-577.

Song, B-H., Wang, X-Q., Li, F.-Z. & Hong, D.-Y. 2001. Further evidence for paraphyly of the Celtidaceae from the chloroplast gene matK. Plant Systematics and Evolution 228: 107-115.

Todzia, C.A. 1993. Ulmaceae. In: K. Kubitzki, J.G., Rohwer & Bittrich, V. (eds). The families and genera of vascular plants, pp. 603-611. Springer-Verlag, Berlin.

Torres, R.B. 1996. Biologia da reprodução de Trema micrantha (L.) Blume (Ulmaceae). Tese de Doutorado. Campinas: Universidade Estadual de Campinas.

Torres, R.B. & Luca, A.Q. 2005. Ulmaceae. In: M.G.L. Wanderley, G.J. Shepherd, T.S. Melhem & A.M. Giulietti (coord.). Flora Fanerogâmica do Estado de São Paulo, pp. 361-369. Fapesp & Rima, São Paulo.

Ueda, K., Keiko, K. & Tobe, H. 1997. A molecular phylogeny of Celtidaceae and Ulmaceae (Urticales) based on rbcl nucleotide sequences. Journal of Plant Reseach 110: 171-178.

Wiegrefe, S.J., Systma, K.J. & Guries, R.P. 1998. The Ulmaceae, one family or two? Evidences from chloroplast DNA restriction site mapping. Plant Systematics and Evolution 210: 249-270.

Cannabaceae, C. M. Wilmot-Dear. Flora Zambesiaca 9:6. 1991

Morphology General Habit

Herbs, annual or perennial, erect or climbing, without latex

Morphology Leaves

Leaves alternate or opposite, petiolate, simple and undivided to palmately lobed or digitately compound; stipules free or fused

Morphology Reproductive morphology Inflorescences

Inflorescences numerous and axillary, flowers dioecious and wind-pollinated Female inflorescences strobilate, flowers ± sessile, crowded, tightly enclosed or loosely subtended by small or large persistent bracteoles; bracts present; perianth membranaceous, entire, investing the ovary; ovary superior, sessile, 1-locular; ovule 1, pendulous, anatropous; style terminal, short; stigmas 2, long filiform Male inflorescences paniculate, flowers with perianth uniseriate, 5-lobed, imbricate; stamens 5, opposite the perianth lobes, anthers straight, erect in bud, 2-thecous, dehiscing at first by apical pores but soon also lengthwise; pistillode absent

sex Male

Male inflorescences paniculate, flowers with perianth uniseriate, 5-lobed, imbricate; stamens 5, opposite the perianth lobes, anthers straight, erect in bud, 2-thecous, dehiscing at first by apical pores but soon also lengthwise; pistillode absent

sex Female

Female inflorescences strobilate, flowers ± sessile, crowded, tightly enclosed or loosely subtended by small or large persistent bracteoles; bracts present; perianth membranaceous, entire, investing the ovary; ovary superior, sessile, 1-locular; ovule 1, pendulous, anatropous; style terminal, short; stigmas 2, long filiform

Morphology Reproductive morphology Fruits

Fruit an achene covered by the persistent perianth; endosperm sparse, fleshy and oily; embryo curved or spirally coiled

Cannabinaceae, Hutchinson and Dalziel. Flora of West Tropical Africa 1:2. 1958

Morphology General Habit

Erect or scandent herbs

Morphology Leaves

Leaves alternate or opposite, simple, undivided or more or less palmately lobed; stipules present

Morphology Reproductive morphology Flowers

Flowers dioecious, axillary, male paniculate, female sessile, crowded or strobilate, with large persistent bracts Female flower: calyx closely enveloping the ovary, entire; ovary sessile, 1-celled; style 2-partite Male flower: calyx 5-partite, segments imbricate; petals absent; stamens 5, erect in bud; anthers 2-celled

sex Male

Male flower: calyx 5-partite, segments imbricate; petals absent; stamens 5, erect in bud; anthers 2-celled

sex Female

Female flower: calyx closely enveloping the ovary, entire; ovary sessile, 1-celled; style 2-partite

Morphology Reproductive morphology Flowers Gynoecium

Ovule solitary, pendulous

Morphology Reproductive morphology Fruits

Fruit an achene, covered by the persistent calyx

Morphology Reproductive morphology Seeds

Seed with fleshy endosperm and curved or spiral embryo