GENUS 33. 



MUSTARD FAMILY. 



'83 



Rock-cress. 



2081. 



13. Arabis Holboellii Hornem Holboell's 



A. Holboellii Hornem. Fl. Dan. n : pi 1879 1827. 

 Arabis rctrofracta Graham, Edinb Phil. Journ. 



1829: 344. 1829. 



Erect, simple or branching above, io'-24' 

 high, stellate-pubescent, hirsute or even nearly 

 glabrous. Lower leaves spatulate or oblanceo- 

 late, tufted, petioled, -2' long, obtuse, entire 

 or sparingly toothed, more or less long-pubes- 

 cent and ciliate; stem-leaves sessile, erect, 

 clasping by a narrow auricled base ; pedicels 

 slender, reflexed or the upper ascending, 3"~5" 

 long in fruit; flowers purple or whitish, 3"-4" 

 long, becoming pendent; petals twice the length 

 of the calyx; pods linear, i'-2' long, slightly 

 more than \" wide, at length reflexed ; seeds 

 margined, in 2 rows in each cell ; style very 

 short or none. 



Greenland to Quebec, Lake Superior, Alaska 

 and British Columbia. Summer. 



14. Arabis Collinsii Fernald. Collin's 

 Rock-cress. Fig. 2082. 



A. Collinsii Fernald, Rhodora 7: 31. 1905. 



Perennial, similar to Arabis Holboellii, but the 

 basal and lower leaves are finely and densely 

 stellate-pubescent. Stems slender, i high or less, 

 erect, glabrous and glaucescent above, densely 

 pubescent near the base ; basal leaves oblanceolate 

 to obovate, petioled, tufted, i'-i' long; stem-leaves 

 lanceolate, acute at apex, sagittate at base ; flow- 

 ers 2"-2\" long; fruiting pedicels 2*"-4" long, 

 strongly reflexed; pods linear, i'-if long, about 

 \" wide, acute or acutish ; seeds narrowly winged 

 above, in 2 rows in each cell. 



On dry limestone rocks, Rimouski County, Que- 

 bec. June-July. 



34. CARDAMINE [Tourn.] L. 

 Sp. PI. 654. 1753. 



Erect or ascending herbs, with scaly or bulbiferous rootstocks, or fibrous roots, entire 

 lobed or divided leaves, and racemose or corymbose white or purple flowers. Stamens 6, 

 rarely 4. Siliques elongated, flat, generally erect; elastically dehiscent at maturity; valves 

 nerveless or faintly nerved. Stipe none. Seeds in I row in each cell, compressed, margin- 

 less; cotyledons accumbent, equal or unequal. [Greek, heart-strengthening, a name for some 

 cress supposed to have that quality.] 



A genus of about 125 species, natives of the temperate regions of both hemispheres. Type 

 species: Cardamine pratensis'L. 



* Leaves pinnately divided, or some of them of but a single terminal segment. 

 Flowers 6"-g" broad, white or purplish; perennial. i. C. pratensis: 



Flowers i" 4" broad, white. 



Leaf-segments numerous, small, the terminal one 2"-io" wide, narrowed, rounded or subcor- 



date at the base ; annuals or biennials. 

 Leaves nearly all b-;al, pubescent. 

 Stem leafy ; leaves glabrous or very nearly so. 



Flowers z"-2y 2 " wide ; plants of swamps, streams ; or wet grounds. 

 Segments of basal leaves 2"-! 2" wide ; plant 8'-3 tall. 

 Segments of basal leaves J/"-i }j" wide ;_ plant 6'- 12' tall. 

 Flowers i"^i l / 2 " wide; plant of dry rocky situations. 



C. hirsuta. 



C. pennsylvanica, 

 C. aren icola. 

 C. parviflora. 



Leaf-segments few large, the terminal one i'-2 f wide, deeply cordate ; perennial. 



6. C. Clematitis. 



** Leaves entire, toothed, or rarely with i or 2 lateral segments; perennials. 



Dwarf, alpine ; leaves nearly entire, long-petioled. 7- C. bellidifolia. 

 Erect or decumbent ; leaves more or less toothed or lobed. 



Flowers purple ; stem erect, from a tuberous base. 8. C. Douglassn. 



Flowers white. r , ., 



Stem erect from a tuberous base. 9- .. &* oosa. 



Stem decumbent, stoloniferous ; roots fibrous. 10. C. rotundifolia. 



