Arabis divaricarpa

 Purple Rock Cress

Basal Leaf Bottom

West Block, Cypress Hills
04-June-2005

Note the trifurcate hairs.

The keys in Budd's Flora and Flora of Alberta are somewhat confusing with respect to the width of the siliques.  The key to the species in Budd's Flora requires:

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siliques 1-2 mm wide; NOT 1.5-2.5 mm wide

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siliques 1-2 mm wide; NOT 2-3.5 mm wide

The key to the species in Flora of Alberta requires:

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siliques generally more than 1.5 mm wide; NOT [less than 1.5 mm wide]

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siliques 1-2.5 mm broad; NOT 2-3 mm broad

According to Flora of the Great Plains, the siliques are 1.25 to 2.5 mm wide.  The siliques of this specimen are 1.8 mm wide.  The rest of the answers to the key questions are listed below.

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Divaricarpa:  Answers to key questions in Budd's Flora and Flora of Alberta leading to this species.  
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plants 20-80 cm high and usually well over 30 cm; NOT 10-20 cm high

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hairs of the lower stems and leaves predominantly trifurcate; NOT simple, NOT malpighian, NOT bifurcate, NOT more freely branched than trifurcate, NOT dendritic

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basal leaves NOT felty

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siliques in part descending, in part spreading, in part ascending; NOT [always sharply reflexed and pendulous], NOT always erect

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siliques 5-10 cm long; NOT 1-5 cm long

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seeds mostly uniseriate; NOT biseriate

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wing of seed mostly over 0.3 mm wide; NOT [less than 0.3 mm or wingless]

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wing of seed 0.5 mm wide or less; NOT nearly 1 mm wide

 
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Arabis: Answers to key questions in Budd's Flora and Flora of Alberta leading to this genus.  These answers do not apply to all members of Arabis found in the Canadian prairies, but they do apply to this species.
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plants pubescent, NOT glabrous

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plants with pubescence mostly or entirely of branched hairs; NOT [plants glabrous, or the pubescence of simple hairs]

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plants generally NOT glaucous

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leaves more or less entire; NOT [deeply serrate to pinnate]

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cauline leaves auriculate, clasping

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flowers much smaller than 20-25 mm across

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petals white, pink-tinged, pink or purple; NOT yellow

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pods strongly flattened; NOT [terete or nearly so]

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pods NOT compressed at right angles to the central partition

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pods scarcely beaked; NOT with a long, distinct beak

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pods usually at least 4 times longer than broad; NOT [2-3 times longer than broad or shorter]

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central partition entire; NOT [with an opening sometimes almost reduced to the margin] 

 
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Cruciferae: Answers to key questions in Budd's Flora leading to this family.
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herbs; NOT [shrubs or trees]

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plants terrestrial or semiaquatic; NOT [plants aquatic, leaves submerged or floating]

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plants NOT with colored milky juice

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plants with more than one normal leaf

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some or all leaves alternate; NOT [leaves opposite, whorled, or basal]

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leaves without stipules, or having glands; NOT [leaves with stipules]

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flowers with two floral rings, and with each petal distinct from the others

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calyx regular

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sepals 4

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corolla regular in shape

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petals 4; NOT 5

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stamens usually 6, four long and two short; NOT [stamens 6, of equal length]

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carpels 1 or 2; NOT 3-5

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ovary superior; NOT inferior