Sisymbrium. CRUCIFERyE. 137 



have not yet been found to exclude from it various species of western and Mexi- 

 can Sisymbria with branched hairs, but much less divided foliage, and connecting 

 with others of South America still more nearly of the Eusisymhrium type. The 

 pubescence, which if all species of both continents are considered passes from 

 simple or occasionally forked hairs to dense stellation, fails to give a really satis- 

 factory generic distinction. In view of the paucity of good technical characters 

 for its subdivision, it seems best therefore to retain the genus in its comprehen- 

 sive sense, the closer afHnities of its species being more conveniently and just as 

 clearly indicated by subgenera and sections. Sharp limitation from Thelypodium 

 is most difficult. The orientation of the stigma-lobes, brought forward by Prantl, 

 is unsatisfactory, since the stigma is so nearly circular in many species of both 

 genera that distinction is impossible, and in at least one species ( T. elegans) of 

 obvious thelypodioid habit and affinities, the stigma-lobes lie over the placentae. 

 The color of the flower ranges from white to yellow in Sisymbrium (as here 

 limited) and in Thelypodium from cream-color to deep purple (in the exceptional 

 T. aureum, deep yellow). The problematic aS'. salsugineuvi, Pall., with glabrous 

 entire cordate-clasping leaves, purplish flowers, and undivided stigma, may well 

 be referred to Thelypodium, from which it appears to be distinguished only by 

 its small size and slender habit. — Inst. 225, t. 109 ; L. Gen. no. 547 ; DC. 

 Syst. ii. 458; Reichenb. Ic. Fl. Germ. ii. t. 72-80; Gray, Gen. 111. i. 151, 

 t. 64 ; Fournier, Recherches sur Fam. Crucif. et Gen. Sisymb. Descurainia & 

 Pachypodium, Webb & Berth. Phyt. Can. i. 72, 74. Stenophragma, Celak. Flora, 

 1872, 438. [By B. L. Robinson.] 



§ 1. Velarum, DC. Siliques subulate, tajjering almost from the base to the 



apex : stigma slightly 2-lobed : pubescence of simple hairs : leaves pinnatifid. — 



Syst. ii. 459. Ghamceplium, Wallr. Sched. Crit. i. 376. — An Old World type 



represented in America by a single species widely introduced. 



S. OFFICINALE, Scop. (Hedge Mustard.) Sleucler, erect, somewliat hirsute near the base, 

 less frequently pubescent throughout : leaves slender-petioled ; segments toothed ; the 

 uppermost leaves narrow, lanceolate, subentire or hastate at the base : racemes spiciform 

 and with 2 to 7 divaricately spreading branches : flowers small, pale yellow : pods on very 

 short erect pedicels. — Fl. Carn. ed. 2, ii. 26; Torr. & Gray, Fl. i. 91 ; Eeichenb. Ic. Fl. 

 Germ. ii. t. 72. '? S. Niagarens^e, Fourn. Sisymb. 85, fide Gray, Am. Jour. Scl. ser. 2, xlii. 

 278. Erijsinmm officinale, L. Si)ec. ii. 660. — Roadsides and waste places, very common. 

 (Nat. from Eu.) 



§ 2. EusiSTMBRiUM, Gren. & Godr. Leafy-stemmed : siliques cylindrical, 

 prismatic, or tapering both ways : stigma usually slightly bifid : pubescence of 

 simple hairs or none, never glandular : leaves entire to pinnatifid. — Fl. Fr. i. 95. 



8. AL'rfssiMUM, L. (used comprehensively to include S. sinajnstrum, Crantz, & S. Pan- 

 nonicum, Jacq.), with runcinate-])innatifid leaves and long firm spreading pods (at maturity 3 or 

 4 inches in length), is scarcely more than a ballast-weed, about the large cities of the Atlantic 

 seaboard ; but has been found occurring .sparingly in S. Missouri, Bush. (Adv. from Eu.) 



S. Irio, L., with runcinate-pinnatifid leaves and slender pods of delicate texture (about an 

 inch and a half in length), is said to be locally established in some parts of the S. E. Atlantic 

 States. (Adv. from Eu.) 



* Leaves lyrately or runcinately pinnatifid, petiolate ; petioles with auriculate stipuliform 

 appendages at the base. 



