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Aquatic and Wetland Vascular Plants of the Northern Great Plains

Rorippa Scop. -- Yellow cress


Annual, biennial or perennial herbs, glabrous or variably pubescent. Leaves often forming a basal rosette in young plants, short-petiolate to sessile, simple, often deeply sinuate, pinnatifid or pinnately lobed to divided, otherwise entire, irregularly serrate, repand or laciniate. Flowers minute or small, yellow or yellowish-green; green to yellowish, deciduous by fruiting time; petals yellow, often fading to whitish when dried, obovate to oblanceolate or spatulate, considerably shorter than to longer than the sepals. Siliques 2 (4)-valved, linear-elongate or more often cylindrical to globose, the seeds crowded in 2 irregular rows.

References:

Booth, W. E. and J. C. Wright.  1959. Rorippa.  Page 95 in Flora of Montana.  
     Part II.  Department of Botany and Microbiology, Montana State University, 
     Bozeman. 

Mulligan, G. A. and A. E. Porsild.  1966. Rorippa calycina in the Northwest         
     Territories.  Canad. J. Bot. 44:1105-1106. 

Stuckey, R. L.  1972.  Taxonomy and distribution of the genus Rorippa in North      
     America.  Sida 4:279-430.

Lead Characteristic Go To
1 Petals shorter than or equal to the sepals. Lead 2
1 Petals longer than the sepals. Lead 5
2 Oldest siliques on the lower portion of the terminal raceme; petals usually longer than 1.2 mm; plants stout and erect, rarely decumbent or prostrate. R. palustris
2 Oldest siliques on lower axillary racemes, or siliques nearly equal in age at corresponding points on the terminal and lateral racemes; petals usually shorter than 1.2 mm; plants prostrate to decumbent and spreading, seldom erect. Lead 3
3 Plants mostly shorter than 3 dm, prostrate to decumbent; pedicels ascending to divergent; siliques truncate to obtuse or acute at the apex (where the style adjoins), but if acute, then the valves minutely papillate; leaves mostly lobed to the middle or nearly so. Lead 4
3 Plants mostly taller than 3 dm, prostrate, decumbent or erect; pedicels ascending or strongly recurved, sometimes so that the raceme appears 1-sided; siliques acute to obtuse or sometimes truncate at the apex, the valves glabrous; leaves mostly entire to irregularly serrate or repand, only the lower deeply lobed. R. curvipes
4 Siliques and usually the pedicels rough with minute papillae, the silique body tapering to the style, not constricted at the middle; leaves lyrate-divided, the margin of the lobes entire. R. tenerrima
4 Siliques and pedicels glabrous, the silique body not at all or only slightly tapering to the style, obtuse to truncate at the apex, constricted near the middle; leaves mostly pinnately divided to the midrib, the margin of the lobes angularly toothed. R. truncata
5 Stems decumbent to prostrate; leaves and stems with few to many hemispherical trichomes or slender, pointed trichomes; leaves sinuate-lobed or pinnatifid. Lead 6
5 Stems erect; leaves and stems glabrous, puberulent or sparsely hirsute; leaves unlobed except for the auriculate base, or pinnately divided to the midrib. Lead 7
6 Trichomes hemispherical on stems, lower leaf surfaces and sometimes on pedicels and siliques; siliques short to elongate-cylindrical with a pointed apex, (2.5)4-8X longer than wide; sepals caducous in fruit. R. sinuata
6 Trichomes elongate and pointed on stems, lower leaf surfaces and sometimes on pedicels and siliques; siliques oblong to subglobose with a rounded apex, 1.3-2.3X longer than wide; sepals persistent in fruit. R. calycina
7 Cauline leaves pinnately divided to the midrib; siliques linear-elongate, 5-10 mm long. R. sylvestris
7 Cauline leaves unlobed except for the auriculate-clasping base, otherwise irregularly serrate; siliques globose, 1-2 mm long. R. austriaca


22. Brassicaceae, the Mustard Family
4. Rorippa Scop. -- Yellow cress
1. Rorippa austriaca (Crantz) Bess. -- Austrian field cress
2. Rorippa calycina (Engelm.) Rydb.
3. Rorippa curvipes Greene
4. Rorippa palustris (L.) Bess. -- Bog yellow cress
5. Rorippa sinuata (Nutt.) A.S. Hitchc. -- Spreading yellow cress
6. Rorippa sylvestris (L.) Bess. -- Creeping yellow cress
7. Rorippa tenerrima Greene
8. Rorippa truncata (Jeps.) Stuckey


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