STRUCTURE OF THE B'ORMATION 63 



and styles are reciprocally of two lengths (heterodistyly), 

 xenogamy alone being possible. 



Carex meadii frequents low prairies and meadows. Its in- 

 dividuals are somewhat aggregated on account of rootstalk 

 propagation. Its bluish green leaves and large, yellow stam- 

 inate spikes appear where there is little else to relieve the 

 monotone left by winter. Carex meadii does not occur widely 

 distributed, nor does it exceed copious 4 in abundance. The 

 copious pollen of the exserted stamens is borne above the pis- 

 tillate spikes, and matures before the stigmas are receptive 

 (proterandry). Allogamy, consisting of xenogamy or geito- 

 nogamy, results. Sisyrinchium angustifolium, a grass-like 

 plant in appearance, occurs typically in low prairies, but is 

 also found in meadows. Its "bunch" habit, causing the small 

 blue and white flowers to be aggregated, renders it conspicu- 

 ous, especially since it appears before the facies play any 

 part in the aspect. The flowers of Sisyrinchium are herko- 

 gamous, the stigmas projecting beyond and alternating with 

 the extrorse anthers, and hemeranthous, opening at 8 a.m. 

 and closing at 5 :30 P.M. They remain closed on cloudy days. 

 It is to be noted that almost every ovary is fertile. Senecio 

 integerrimus is conspicuous on account of being represented 

 in the formation by one individual. 



Senecio plattensis is met rarely in the low prairies. Its 

 numerous bright yellow heads, especially when the individu- 

 als are semi-aggregated, as is usually the case, are conspicu- 

 ous objects of the early vernal period. Wind dissemination 

 obtains by means of the copious pappus. Both Senecio plat- 

 tensis and S. integerrimus produce open rosettes through 

 the agency of which these plants secure greater recognition on 

 account of blossoming earlier. 



Fragaria virginiana haunts low prairies and meadows, 

 where, on account of numerous runners, it forms rather defi- 

 nite patches, of which two or three are observed in the forma- 

 tion. Fragaria forms open rosettes, the inner silky leaves of 

 which are covered over with the broad stipules of the outer 



