CRTJCIFEBJE. 13 



Ordbbvii. CRUCIFER/E. 



Herbaceous or rarely suffruitescent plants with watery pungent juice, 

 alternate exstipulate leaves, and usually racemose white or yellow or 

 sometimes purple flowers. Sepals 4, imbricate, deciduous. Petals 4, 

 often unguiculate, the laminae spreading in the form of a cross (unequal, 

 and differently arranged in many of our Streptanlhi), hypogynous, 

 deciduous. Stamens almost always tetradynamous, i. e., 4 long, 2 short 

 (except in some Streplanthi, where they are in 3 unequal pairs, and in 

 Athysanus and Heterodraba, which have them all of equal length); in 

 some species reduced to 4 and even 2, hypogynous. Fruit usually a 

 silique or silicle of 2 valves which separate from a central partition 

 formed by the united placentas. Seeds attached to the outer edge of the 

 partition all around, usually forming a single row under the valves. 



* Pods indehiscent. 



Pods l-seeded, not wing-margined Athysanus 3 



" wing-margined Thysanocarpus 17 



. . * «„*...„ „j i short and rounded, Heterodraba 2 



sereral-seeded, flattened } lin V elongated... Tropidooarpum 21 



" " terete and pointed Bhaphanus 19 



, , + , ■ ,.„ 5 2 dissimilar l-seeded joints .. Cakile 20 



breaking transversely into | ee yeral l-seeded joinM Rhaphanus ID 



formed of 2 opposite l-seeded nutlets Uoronopus. 18 



* * Pods dehiscent from below. 



Podsobovoid, scarcely compressed Camelina 4 



" orbicular, flattened parallel with the partition Alyssum 1 



" flattenedcontrarytothepartition} S^^rV/SiuM 11 



" oblong, linear-oblong, or slender- ( fl. white Nasturtium 9 



conical, turgid, slightly curved ( fl. yellow Boripa 10 



thin-walled, straight Sisymbrium 14 



" i,-„„o, i „».™ioj ( leaves lyrate Barbarea 11 



linear, 4-angled } leaves entire or ruI10 i nat e Erysimum 12 



'■ '•■ ta ^« (beaked Brasstoa 13 



lerece } D eakless Thelypodium 7 



** " compressed; valves elaBtically dehiscent Cardamine 8 



„ „ _ „„ „j _ ,.„i„„ t ;„ ( claw of petals narrow Arabis 5 



compressed; not elastic | „ "„ broad Strkptanthus B 



* * * Pods dehiscent from the apex. Tropidooarpum 21 



I. ALYSSUJI, Diose. Low herbs with simple leaves and more or 

 less of a stellate pubescence. Sepals equal. Petals white or yellowish. 

 Pod orbicular; valves convex, nerveless. Seeds 1 or 2 in each cell. 



1. A. alyssoides (L.), Gouan. Annual, branching from the base, 

 decumbent, ^ —1 ft. high, canescenl: leaves linear-spatulate, }4~1 in. 

 long: raceme rather slender, the white or pale yellow petals Utile exceed- 

 ing the sepals: pod slightly emarginate, little exceeding the persistent 

 sepals, 4-seeded.— Naturalized about San Francisco. 



