68 KEY AND FLORA 



radiating from the seed to the margin. Erect, branching, 

 annual herbs, with leaves sessile and generally auriculate- 

 clasping. 



a. T. curMpes Hook. This is the commonest species. It has the 

 fruit with crenate margin, often perforated. Widely distributed. 



b. T. ra'dians Benth. This has much larger fruit than the preced- 

 ing, with lines radiating from the center to the outside of the wing. 

 This is found from California to Oregon. 



H. ATHY'SANUS 



Flowers very small. Fruit roundish, not winged, generally 

 covered with hooked prickles, indehiscent and 1-seeded. Low, 

 spreading, slender, delicate, hairy herbs, fruiting in spring. 



A. pusil'lus Greene. This is the only species. It is widely 

 distributed. 



HI. LEPID'IUM, Peppergrass 



Flowers small, white or greenish, with petals often want- 

 ing. Fruit roundish, usually notched at the apex, 2-celled, 

 flattened contrary to the partition. 



a. L. nit'idum Nutt. Low annuals. Pods shining, reddish, very 

 numerous. Leaves compound, with narrow, linear leaflets. This is 

 one of the earliest plants of spring. Widely distributed. 



b. L. bipinnatif'idum Desv. Low, almost prostrate herbs, with 

 the lowest leaves twice divided, and divisions usually roundish. 

 Petals wanting. Pods round, on stout spreading pedicels. Introduced; 

 Common on roads and streets. 



c. L. apet'alum Willd. Stems slender, a foot or so high, branch- 

 ing. Lower leaves toothed or more deeply divided, acute at apex. 

 Flowers without petals, on erect pedicels that spread widely in fruit. 

 Pods smooth, round, notched at apex. This is a weed which has been 

 introduced and is now widely distributed. 



IV. SENEBIE'RA, Wart Cress 



Flowers greenish. Pod of 2 globose, equal parts united, form- 

 ing a twin pod. Leaves pinnately parted. Low, spreading, 

 introduced plants with a disagreeable odor. 



