352 IOWA ACADEMY OF SCIENCE 



and covered with stout hooked spines ; two seeds in each fruit ; 

 seeds are brown to black and flattened spindle-shaped. 0., com- 

 mon in waste lands. Native. 



89. Xanthium spinosum L. Cocklebur. Like the preceding 

 species but about one-half the size and with much weaker spines. 



90. Heliopsis kelianthoides L. Sweet Ox-eye. L., 4. — 6.4 

 mm. W., 1.8 — 2.6 mm. C, brown to straw-colored. S.. oblong 

 wedge-shaped usually very prominently four-angled ; tapering 

 at the base and abruptly cut off at the apex ; with a very low 

 collar or elevation at the apex. 0., quite common. Native. 



91. Budbeckia hirta L. Black-eyed Susan, Yellow Daisy. 

 L., 1.5 — 2. mm. W.. .3 — 5 mm. C, dark brown to black. S., 

 somewhat four-angled ; tapering from apical end to the base ; 

 apex concave; with twenty to thirty fine longitudinal lines 

 composed of numerous small brick-shaped scales placed side by 

 side. 0., quite widely distributed and found chiefly in tim- 

 othy seed. Native. 



92. Helianthus divaricatus L. "Wild Sunflower. L., 3.8 — • 

 6.5 mm. W., 1.8 — 2.2 mm. C, brownish black, sometimes gray. 

 S., obovate and slightly four-angled; pointed at one end. 0., 

 common in waste places, thickets, etc., also in alfalfa seeds. 

 Native. 



93. Bidens frondosa L. Beggar's ticks. L., 5 — 15 mm. W., 

 2 — 4 mm. C, dull brown blotched with black. S., diamond- 

 shaped in cross section ; much flattened ; with two or some- 

 times three slightly diverging awns at the apical end. 0., com- 

 mon in waste land. Native. 



94. Bidens cernua L. Sticktight. L., 3.8—6.4 mm. W., 1.4—3. 

 mm. C, dark greenish or grayish brown. S., somewhat wedge- 

 shaped, four sided with a slight groove on each face and four 

 awns at the apical or broader end. 0., quite common. Intro- 

 duced from Europe. 



95. Galinsoga parviflora Cav. L., 1.2 — 1.6 mm. W., .5 — .7 mm. 

 C, dark gray or brown with numerous silvery hairs. S.. some- 

 what pyramid-shaped with four sides; broadest towards the 

 apex; surface covered with short (.2 mm.) upward pointing 

 hairs and crowned at the apex with a fairly persistent row of 

 white chaffy bristles. 0., becoming rapidly abundant about 

 Ithaca, New York; introduced near the Agricultural College 

 about 1907. Native of tropical America. 



