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5. IDENTIFICATION KEYS FOR SPECIES OF PROSOPIS

The identification keys to Prosopis in Mexico, Chile and Peru that follow have been modified from the key developed by Simpson et al. (1975) to include, by country, the major species found in that country. These keys are intended only as guides. Due to the normal variation encountered between individuals, samples from several plants should be studies and compared with the descriptive information for the individual species provided in the section in this handbook which follows the Keys. The nomenclature of the principal plant parts is shown in Figures 1 and 2.

5.1 Identification key to major Prosopis species in Mexico

1a Spines beige or brown arising above a leaf cluster or solitary and axillary. Inflorescence a spike or slender catkin. Pods straight or loosely spiraled, usually somewhat flattened.

2a Pod straight without visible beading or with inconspicuous restrictions.

3a Leaflets linear, over five times as long as wide or longer than 20 mm. Pod straight rarely curved, yellow or tinged with violet. Distribution: northeastern Mexico.

(1) P. glandulosa (see page 17 of this handbook)

3b Leaflets oblong less than five times as long as wide or 15 to 20 mm long. Pod straight with incurved apex, sometimes curved, yellow to brown. Distribution: southern Mexico.

Table 1

Classification of major Prosopis species

FAO (1980) Most recent classification
 Mexico 
P. juliflora=P. juliflora
P. torreyana=possibly P. glandulosa and/or P. glanulosa var. torreyana
P. alba=P. alba, not native but may be introduced into Mexico
 Chile 
P. tamarugo=P. tamarugo
P. chilensis=P. chilensis
P. siliquastrum=P. siliquastrum
P. burkartii=P. burkartii
P. atacamensis=P. alba
 Peru 
P. chilensis=P. chilensis
P. limensis=P. pallida
P. juliflora=P. juliflora

Table 2

Prosopis species by country

Mexico    ChilePeru
P. julifloraP. tamarugoP. chilensis
P. pubencensP. chilensisP. pallida
P. palmeriP. burkartiiP. juliflora
P. articuladaP. albaP. juliflora var. horrida
P. tamaulipanaP. alba var. pantaP. juliflora var. inermis
P. laevigataP. flexuosaP. strombulifera
P. glandulosa P. reptans
P. glandulosa var. torreyana P. laevigata
P. velutina P. alba var. panta

Figure 1. Nomenclature of the leaf and spines of Prosopis.

LEAF

Figure 1
Figure 1Figure 1Figure 1
Paired axillary SPINESSolitary nodal SPINESSPINES formed from hardened stipules

Figure 2. Nomenclature of the flower and fruit of Prosopis.

FLOWERINFLORESCENCE
Figure 2Figure 2
Figure 2Figure 2
LEGUME

(2) P. juliflora (see page 18)

2b   Pod slightly beaded to constricted, usually speckled.

4a   Leaves expanded, usually longer than the inflorescences.

5a   Leaflets 4 to 6.3 mm long, linear or oblong.

6a   Leaflets pubescent, almost or actually touching, 5 to 15 mm long, 12 to 30 pairs per pinna. Immature fruit pubescent. Joints of the pod about as long as wide. Distribution: northwestern Mexico along U.S. border.

(3) P. velutina (see page 27)

6b   Leaflets ablong with the mid-veins of the leaflets less visible and contrasting in color, glabrous or slightly ciliate along the margins, 7 to 63 mm long, widely separated along the rachis. Joints on the pod wider than long.

7a   Leaflets more than five times as long as wide, stiff, leathery. Plants often shruby. Distribution: northern Mexico.

(4) P. glandulosa var. torreyana (see page 18)

7b   Leaflets less than five times as long as broad, herbaceous, relatively soft. Usually trees. Distribution: coastal areas of Mexico.

(5) P. juliflora (see page 18)

5b   Leaflets elliptical, oblong, glabrous, less than 10 mm long, conspicuously veined, spaced at distances along the rachis less than the width of a leaflet. Pods are thick, pure yellow and slightly beaded. Distribution: the central plateau and hillslides of northern Mexico.

(6) P. laevigata (see page 20)

4b   Leaves small, shorter than or equal to the length of the inflorescence.

8a   Pod dry, thin, flexible and smooth, constricted between the segments, and whitish in color. Leaves with one or two pairs of pinnae and 6 to 20 pairs of leaflets. Distribution: northwestern Mexico and Baja peninsula.

(7) P. articulata (see page 14)

8b   Pod fleshy, straight, slightly flattened but thick, narrow (6 to 8 mm wide), and straw-yellow in color. Leaves with 1 to 3 pairs of pinnae and 20 to 29 pairs of leaflets. Distribution: States of Tamaulipas and Veracruz, Mexico.

(8) P. tamaulipana (see page 26)

1b   Spines are paired and white or yellow, arising from underneath a leaf cluster and formed by stipules that have become spiny. Inflorescences in round heads or in open stubby spikes. Pods coiled or short, stubby and arched. Leaves always with only one pair of pinnae and small leaflets.

9a   Pods pointed and arched or coiled.

10a Inflorescence an open spike. Pod smooth, slightly flattened, pointed and arched. Distribution: native to Baja peninsula.

(9) P. palmeri (see page 22)

10b   Inflorescence a round ball about 1 cm in diameter. Pods with more than five irregular coils. Leaflets almost overlapping, usually 6 to 12 pairs per pinna, glabrous or pubescent. Distribution: northern Mexico adjacent to Texas border.

(10) P. reptans (see page 24)

9b   Pod smooth with numerous tight, regular coils bound singly or only a few in a cluster. Distribution: Baja peninsula and north-western Mexico.

(11) P. pubescens (see page 23)

5.2 Identification key to major Prosopis species in Chile

1a   Spines beige or brown, paired and axillary. Inflorescence a spikelike raceme. Leaves with 1 to 3 pairs of pinnae. Pods straight or nearly straight to curved, slightly beaded. Leaves usually longer than the inflorescence.

2a   Leaflets linear, large, 10 to 63 mm long, widely separated along the rachis at distances equal to or greater than their width, 10 to 29 leaflets per pinna. Distribution: central Chile.

(1) P. chilensis (see page 15)

2b   Leaflets linear, acute to subacute or obtuse less than 7.5 cm long.

3a   Leaflets linear, obtuse less than 6 mm long, 25 to 50 pairs per pinna, closely spaced at distances less than their width. Spines scarce and small. Pod very nearly straight, and may reach a length up to 30 cm. Distribution: Central-north Chile, Central-south Peru.

(2) P. alba var. panta (see page 14)

3b   Leaflets linear, 6 to 7.5 cm long, 25 to 60 pair per pinna, widely spaced at distances greater than their width. Pod nearly straight or curved, 5 to 28 cm long. Spines rarely as much as 3 cm long, often inconspicuous or absent. Distribution: northern Chile.

(3) P. flexuosa (see page 16)

1b   Spines white or yellow arising from underneath a leaf cluster and formed by hardened stipules. Inflorescences in round heads or in open, stubby spikes. Leaves with only one pair of pinnae. Pods coiled or short, stubby and strongly arched.

4a   Spines white and thin. Seeds arranged end to end in the pod.

5a   Inflorescence an open spike, pods smooth with one to three tight coils. Several pods held in a single cluster. Distribution: Province of Tarapaca, Chile.

(4) P. burkartii (see page 15)

5b   Inflorescence a round ball about 1 cm in diameter. Pods with more than five irregular coils. Distribution: northern Chile.

(5) P. strombulifera (see page 24)

4b   Spines yellow, large. Seeds in the pod arranged horizontally, side to side. Pod curved into one-half or a complete circle. Distribution: Province of Tarapaca, Chile.

(6) P. tamarugo (see page 25)

5.3 Identification key to major Prosopis species in Peru

1a   Flower petals hairy near the tip on the inside. Ovary always hairy or pubescent. Leaflets glabrous or pubescent. Branches with spines.

2a   Spines beige or brown arising above a leaf cluster or solitary and axillary. Inflorescence a spike or slender catkin. Pods straight, usually somewhat flattened. Seeds separated by a stony endocarp.

3a   Leaves expanded usually longer than the inflorescence.

4a   Leaflets 4 to 63 mm long, linear, or oblong.

5a   Leaflets pubescent, elliptical, ovate to oblong, 5 to 15 mm long, 2 to 4.8 mm, wide with conspicuous spaces between pairs along the rachis. Veins in a visible network. Immature fruit glabrous. Pod straight to arched. Distribution: northern Peru.

(1) P. juliflora var. horrida (see page 19)

5b   Leaflets linear, glabrous or only slightly ciliated along the margins, 11 to 54 mm long, 10 to 29 pairs per pinna. Mid-vein of leaflets visible but green, pod broad, nearly straight to sickle shaped. Spines always paired, up to 6 cm long. Distribution: southern Peru.

(2) P. chilensis (see page 15)

4b   Leaflets elliptical, oblong, glabrous, less than 15 mm long, 12 to 30 pairs per pinna. Pod straight and beaded or with parallel edges, slightly flattened, often curved.

6a   Leaflets not conspicuously veined on the underside, 25 to 50 pairs per pinna, separated on the rachis. Pod nearly straight, up to 30 cm long. Distribution: semi-arid areas of Peru.

(3) P. alba var. panta (see page 14)

6b   Leaflets 16 to 24 pairs per pinna, nearly touching on the rachis. Pod arched. Distribution: southern Peru.

(4) P. laevigata var. andicola (see page 21)

3b   Leaves small, shorter than or equal to the length of the inflorescence. Pods slightly flattened, 9 to 16 mm wide but thick with no constrictions between the segments. Leaflets with conspiscious nerves on the underside, obtuse or very rapidly tapering to a narrow point. Spines small or absent. Distribution: native in Peru.

(7) P. pallida (see page 21)

2b   Spines white or yellow arising from underneath a leaf cluster and formed by hardened stipules. Inflorescences in round heads about 1 cm in diameter. Pods yellow with more than five irregular coils. Small shrubs.

7a   Leaflets widely spaced along the rachis. Leaflets glabrous, three to eight pairs per pinna. Distribution: southern Peru.

(5) P. strombulifera (see page 24)

7b   Leaflets close together, almost overlapping, slightly pubescent, 6 to 12 pairs of leaflets per pinna. Distribution: central Peru in the Province of Huancavelica.

(6) P. reptans (see page 24)

1b   Inside of petals hairless. Branches without spines. Leaflets pubescent.

8a   Racemes longer than the leaves. Leaflets 2.5 to 8.3 mm long. Distribution: northern Peru.

(8) P. pallida (see page 21)

8b   Racemes about the same length as the leaves. Leaflets 6 to 20 mm long. Distribution: northern South America.

(9) P. juliflora var. inermis (see page 20)


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