FAMILIES OF PLANTS 
65 
1. Pods at least twice as long as broad. 2. 
1. Pods less than twice as long as broad. 10. 
2. Pods an inch or more long. 3. 
2. Pods less than an inch long. 5. 
3. Flowers yellow or orange. Blistercress ( Erysimum) _(p. 65) 
3. Flowers not yellow or orange. 4. 
4. Pods flattened. Rockcress (Arabis) -(p. 65) 
4. Pods not flattened. Thelypodium -^-(p, 66) 
5. Flowers not yellow. 6. 
5. Flowers yellow. 7. 
6. Plants smooth. Bittercress ( Cardamine) -(p. 66) 
6. Plants hairy. Smelowskia americana __(p. 66) 
7. Leaves dissected. Tansymustard (Sophia) -(p. 66) 
7. Leaves lobed but not dissected. 8. 
8. Pods short, about twice as long as broad. Roripa -(p. 67) 
8. Pods long, several times as long as broad. 9. 
9. Plants smooth. Wintercress ( Barbarea americana )_(p. 67) 
9. Plants rough with scattered hairs. Mustard ( Brassica )-(p. 67) 
10. Pods inflated. Twinpod (Physaria didymocarpa) _(p. 67) 
10. Pods not inflated. 11. 
11. Pods flattened. 12. 
11. Pods not flattened. False-flax (Camelina microcarpa) _(p. 67) 
12. Pods deeply notched at the end. 13. 
12. Pods not notched at the end. 14. 
13. Basal leaves deeply lobed. Shepherds-purse (Capsella bursa-pastoris) _(p. 67) 
13. Basal leaves entire or merely toothed. Thlaspi _(p. 67) 
14. Pods only 1- or 2-seeded. Peppergrass ( Lepidium) -(p. 67) 
14. Pods several-seeded. 15. 
15. Plants growing in shallow water or mud. Awlwort (Subularia aquatica ) 
(p. 68) 
15. Plants not growing in shallow water or mud. 16. 
16. Flowers minute, white. Hutchinsia procumbens _(p. 67) 
16. Flowers not minute, yellow or white. Whitlowgrass ( Draba )_(p. 68) 
Rough blistercress (Erysimum asperum ).—This is one of the most 
conspicuous members of the mustard family with its large, orange- 
yellow flowers. 
Erysimum inconspicuum has much smaller, yellow flowers. Both 
of these species have stems and leaves that are pale from the ap- 
pressed, whitish hairs. 
The Wormseed mustard (Erysimum c heir ant hoides) is similar to 
the latter of the preceding species but is slightly rough-hairy and 
is not made pale thereby. 
Rockcress (Arabis) .—The various species occurring in the park may 
be distinguished in the following manner: 
1. Flowers rose color. 2. 
1. Flowers purple. 4. 
1. Flowers white or whitish. 5. 
2. Plants usually more than 8 inches high. Leaves narrow. 3. 
2. Plants less than 8 inches high. Leaves broader and 
rather thick___________ Arabis lemmonii. 
3. Leaves linear. Pods about 2 inches long__ Arabis miorophylla. 
