248 CRUCIFEE^E, 



some species reduced to 4 and even 2, always hypogynous (except in 

 Suhularia). Fruit usually a silique or silicle of 2 valves which separate 

 from a central partition formed by the united placentae. Seeds attached 

 to the outer edge of the placental partition all around, usually forming a 

 single row under the valves; albumen 0; embryo curved, the relations 

 of radicle and cotyledons various. 



lliiitjit of the Crenera. 



Inflorescence bractless; pods stipitate, -------- 12, 13 



*' " pods not stipitate; 



Pods 2-celled, 2-valved, regtilarly dehiscent from below; 



■' short, flattened parallel with the broad partition, - - 1, 2, 4 



" " flattened contrary to the narrow partition, - - 20 — 23 



" ovoid or globose, or the valves distended, - - - . 3, 7 



" longer, flattened or subterete, or 4-angled, beaked, - 8, 9, 14, 18 

 " long, " " " beakless, 10, 11, 13, 15-17, 19 



" of 2 short opposite indehiscent 1-seeded cells, - - - 25 



" longer, transversely jointed or indehiscent, - . - 26, 27 



" orbicular, 1-seeded, indehiscent, ------ 6, 24 



" ovoid, several-seeded, indehiscent, ------ 5 



Inflorescence leafy or bracted; pods without partition, dehiscent from the 



apex or indehiscent, ----------- 28 



1. PLATYSPERMUM, Hooker. Low annual, with pinuatifid radical 

 leaves, and slender 1-flowered scapes. Flowers very small, white. Silicle 

 oval, about 8-seeded. Seeds flat, with a broad scarious wing; cotyledons 

 accumbent. — The genus Leavenworthia of the Atlantic slope of the Con- 

 tinent is very nearly related to this. 



1. P. scapigerum, Hook. Fl. i. 68. t. 18 (1829). Glabrous, 2—3 in. 

 high: leaves somewhat runcinately pinnatifid: sepals equal, spreading: 

 petals very small, scarcely unguiculate, obovate, white : pods about % in. 

 long. — Sierra Co., Lemmon, and northward, usually in rather moist open 

 ground. Apr. 



2. ALYSSUM, Dioscorides. Low perennials, with simple leaves, and 

 more or less of a stellate pubescence. Flowers racemose. Sepals equal. 

 Petals white or yellowish. Longer filaments often toothed. Pod orbicu- 

 lar; valves convex, nerveless. Seeds 1 or 2 in each cell, slightly 

 margined; cotyledons accumbent. 



1. A. ALYSsoiDES, Gouau, Hort. Monsp. 321 (1762); Linn. Sp. PI. ii. 

 652 (1753), under Clypeola: A. calycinurn, Linn. Sp. PI. 2 ed. ii. 908 

 (1763). Annual, branching from the base, decumbent, i^ — 1 ft. high; 

 herbage canescent: leaves linear-spatulate, }4 — ^ i^- long: raceme rather 

 slender, the white or pale yellow petals little exceeding the sepals : pod 

 orbicular, with a thin margin, slightly emarginate, l^g lines broad, little 

 exceeding the persistent sepals, 4-seeded, on spreading pedicels a line 

 long: style }4 line. — Said to be naturalized about the Bay of San Fran- 

 cisco, but we have not seen it. 



