Juglandaceae DC.ex Perleb

Milliken, W. (2009). Neotropical Juglandaceae.

Morphology

Description

Trees, medium-sized to large.  Leaves pinnately compound with pinnate venation on the lamina , alternate or opposite, sometimes terminating with a single leaflet (Juglans  L.), indumentum of stellate hairs or peltate scales, commonly resinous and aromatic, basal leaflets often significantly smaller than terminal ones; stipules absent. Inflorescences terminal or axillary in the form of catkins, panicles, spikes or solitary flowers.  Flowers unisexual or hermaphrodite , petals absent, sepals 0-4. Male flowers subtended by fused bracts, with 4-100 basifixed sessile or subsessile anthers dehiscing by longitudinal slits. Female flowers with 2 stigmas and sometimes with staminodes, sepals fused to ovary .  Gynoecium syncarpous with 2 carpels.  Fruits are nuts enclosed by fleshy or winglike fused bracts/ perianth , giving a samaroid or drupaceous appearance. Seeds one per fruit .

General Description

Notes on delimitation

• The Juglandaceae are placed in the Fagales by morphological and molecular studies, close to the Betulaceae, Ticodendraceae, Fagaceae and Myricaceae (Manos & Steele, 1997).

Number of genera

Four genera:

• Juglans
• Alfaroa
• Oreomunnea
• Carya

Status

• Native.

General notes

• Some species of Juglans and Carya produce high-quality timber. 
• Several Juglans species also produce edible nuts.

Distribution

Distribution in the Neotropics

• In the Neotropics only one genus, Juglans L., is widespread from Mexico to Argentina. 
• The others (Alfaroa Standl., Oreomunnea Oerst. and Carya Nutt.) are predominantly found in Mexico and Central America (with Alfaroa and Oreomunnea extending into Colombia).

Diagnostic

Distinguishing characters (always present)

• Trees with pinnately compound leaves and unisexual flowers with inferior ovary.
• Gynoecium bicarpellate, with two styles.
• Fruits one-seeded.

Other important characters

• Aromatic and/or resinous leaves.
• Margins of leaflets commonly serrate or serrulate.
• Sometimes with chambered pith in the twigs (Juglans).
• Male flowers in catkins, female flowers often on separate inflorescences.
• Fruits with hard endocarp and ridges or wings.
• Leaflets forming progression from larger terminal to smaller proximal.

Key differences from similar families

• Although closely related to other members of the Fagales, this family is readily distinguished from all of them by its compound leaves.

Useful tips for generic identification

• Juglans : alternate leaves, perianth of 4 sepals, androecium of 7-100 stamens, nut with complex internal structure surrounded by a ridged husk which dehisces, pith in twigs sometimes chambered.
• Alfaroa : opposite leaves, perianth of 2 sepals, androecium of 6-12 anthers, nut without wings and without dehiscent husk.
• Oreomunnea : opposite leaves, perianth of 2 sepals, androecium of 8-25 anthers, bracts and bracteoles fused into winglike (samaroid) structure around nut.
• Carya : alternate leaves, perianth absent, 4 stamens in androecium, nut surrounded by a ridged husk which dehisces.

Key to genera of Neotropical Juglandaceae

1. Leaves opposite ... 2
1. Leaves alternate...3

2. Fruits with samaroid wings ... Oreomunnea
2. Fruits without samaroid wings ... Alfaroa

3. Perianth present in flower... Juglans
3. Perianth absent in flower... Carya

Literature

Important literature

González, F. (2004). Juglandaceae.  pp 196-198 in: Smith, N.A. et al. (eds), Flowering plants of the Neotropics. Princeton University Press, New Jersey.

Manning, W.E. (1960). The genus Juglans  L. in South America and the West Indies. Brittonia 12(1): 1-26.

Manos, P. S. & Steele, K. P. (1997). Phylogenetic analyses of 'higher' Hamamelididae based on plastid sequence data. Amer. J. Bot.84:1407-1419.

Manos, P.S. & Stone, D.E. (2001).  Evolution, systematics and Phylogeny of the Juglandaceae.  Ann. Missouri Bot. Gard.88(2): 231-269.

Stone, D.E. (1972). New World Juglandaceae III. A new perspective of the tropical members with winged fruits.  Ann. Missouri Bot. Gard.59: 297-321.