Exhalimolobos Al-Shehbaz & C. D. Bailey, Syst. Bot. 32: 147. 2007.

Ihsan A. Al-Shehbaz

Tribe: Halimolobeae Al-Shehbaz, Beilstein & E.A. Kellogg, Pl. Syst. Evol. 259. 110. 2006.

Name derivation: from Latin ex (prep.), out of, and Halimolobos, a genus of Brassicaceae, in reference to the species exluded or transferred from it to the present one.

Type species: Exhalimolobos palmeri (Hemsley) Al-Shehbaz & C. D. Bailey (based on Sisymbrium palmeri Hemsley).

     Herbs, biennial or perennial with a woody caudex. Trichomes dendritic or subdendritic, stalked or subsessile, sometimes mixed with fewer or much more simple, subsetose ones. Multicellular glands absent. Stems erect to ascending, rarely decumbent, simple or branched. Basal leaves petiolate, not rosulate, simple, coarsely dentate or sinuate or rarely pinnately lobed, often withered by anthesis or fruiting; cauline leaves short-petiolate or sessile, base auriculate to amplexicaul or not auriculate, margin dentate or sinuate-dentate, rarely pinnately lobed. Racemes corymbose, several to numerous flowered, ebracteate, elongated considerably in fruit; rachis straight; fruiting pedicels ascending to divaricate or recurved, persistent. Sepals oblong, free, erect or rarely ascending, caducous, pubescent, equal, base of lateral pair not saccate. Petals white, rarely pink or with pinkish veins, erect with flaring blade, longer than sepals; blade oblanceolate or spatulate, apex obtuse; claw obscurely differentiated from blade, glabrous, unappendaged, entire. Stamens 6, included, erect or rarely slightly spreading, tetradynamous; filaments filiform, wingless, unappendaged, glabrous, free; anthers ovate or oblong, not apiculate at apex. Nectar glands nectar glands confluent, subtending bases of all stamens, lateral glands usually annular. Ovules 40-270(-300) per ovary; placentation parietal. Fruits dehiscent siliques, linear, terete or slightly angustiseptate, not inflated, unsegmented; valves papery, with a prominent midvein extending at least to middle and distinct marginal veins, pubescent with uniform, subsessile or short stalked dendritic trichomes, rarely glabrous, wingless, not torulose, unappendaged; replum rounded; septum complete, membranous; style distinct, to 3.5 mm, persistent; stigma capitate, entire, unappendaged. Seeds biseriate, wingless, oblong, plump; seed coat minutely reticulate, mucilaginous when wetted; cotyledons incumbent. x = 8.

Nine species: Argentina, Bolivia, Colombia, Ecuador, Mexico, Peru, Venezuela.

References: Bailey et al. (2002, 2007), Rollins (1943). 

                                                                    Key to the species of Exhalimolobos

1. Plants densely pubescent throughout with predominately simple trichomes, branched

     trichomes restricted to leaf margins ……………………………………..........................…...............................…..8. E. polyspermus

1. Plants pubescent with appressed or short-stalked 2-8-rayed trichomes, simple trichomes (if present)

     restricted to lower portions of stems and leaf veins, always fewer than branched trichomes.

2. Fruits and fruiting pedicels appressed to rachis …………………………......................................….....................…..7. E. pazense

2. Fruits and fruiting pedicels descending, horizontal, divaricate, or ascending, never

     appressed to rachis.

          3. Cauline leaves cuneate at base, neither auriculate nor amplexicaul.

4. Fruit glabrescent; style ca. 0.1 mm; seeds 0.4-0.5 mm; Argentina .................................................................. .3. E. burkartii

4. Fruits pubescent; style 0.5-1 mm; seeds 0.7-1 mm; Mexico …................................................................... 2. E. berlandieri

          3. Cauline leaves amplexicaul or auriculate at base.

5. Petals 5-6.5 ´ 1.5-2 mm; fruits horizontal to somewhat reflexed, 2.5-3

     mm wide; style (1-)1.5-2.5 mm ……………………………...……....................................................…..1. E. arabioides

5. Petals 1.5-4(-4.5) ´ 0.3-1.2 mm; fruits divaricate to ascending or erect,

     1-1.7(-2) mm wide; style obsolete or 0.2-1(-1.5) mm.

6. Fruit valves sparsely pubescent on the inside; seeds/ovules 40-60(-84) per

     fruit; fruits 0.4-1.2(-1.5) cm ………………………...............................………….....................………….6. E. parryi

6. Fruit valves glabrous on the inside; seeds/ovules (80-)100-250(-300) per fruit;

   fruits (0.8-)1-3.8 cm.

7. Fruits moderately to densely pubescent; stems without setose trichomes................................................. 9. E. weddellii

7. Fruits glabrous or sparsely pubescent; stems with setose trichomes to 1.5 mm.

8. Fruits glabrous; style obsolete or to 0.2 mm; seeds 0.5-0.6 mm; north-central Mexico ........................5. E. palmeri

8. Fruits sparsely pubescent; style 0.5-1.5 mm; seeds (0.6-)0.7-0.9(-1) mm; south-central

    Mexico, South America...................................................................................................................4. E. hispidulus