STRUCTURE OF THE FORMATION 77 



that very few of the ovaries become fertile. Maturation be- 

 gins September 1, dissemination occurring as for A. verticil- 

 lata. Asclepias syriaca and A. sullivantii are frequenters of 

 low prairies, meadows, and draws, where they occur only 

 rarely; the latter species prefers the wetter situations. A. 

 syriaca also grows in cultivated fields, wastes, and along bor- 

 ders of thickets. The tall, leafy stems, bearing numerous 

 umbels of purplish flowers, are striking objects in the forma- 

 tion. These flowers continue for twenty-five to thirty days, 

 during which time they are visited frequently by the red- 

 brown milkweed butterfly {Danais arcMppus). Dissemina- 

 tion is the same as for other milkweeds. 



The distribution of Baptisia leucantha has already been 

 indicated. The plant is found but sparsely in low prairies 

 and meadows ; nevertheless it is a conspicuous element of the 

 floral aspect. The erect stems develop from a perennial root 

 and are crowned with a long, loosely flowered raceme of 

 cream-colored flowers, which continue during June, After 

 anthesis these plants give the appearance of miniature trees 

 scattered throughout the formation. Fertilization obtains 

 through the agency of bumble bees and is in all respects as 

 for B. bracteata. The inflated pods mature during the latter 

 part of July, but give no clue to methods of dissemination. 

 Meibomia iUinocnsis, a tall, rigid, branching perennial, one to 

 two meters high, abounds at a few stations in the low prairies, 

 meadows, and draws. It ordinarily averages 25-60 individu- 

 als to the five-meter plot ; however, in one quadrat 672 plants 

 were enumerated. In this particular case, Meibomia has be- 

 come a controlling element in the formation, either crowding 

 out or subordinating the secondary species. The long raceme 

 of light blue flowers is especially noticeable during the 

 morning hours. The easily separable loments are bristly 

 uncinate-pubescent, and adhere to any surface with which 

 they come in contact. Ly thrum alatum inhabits ravines, 

 draws, and wet meadows. It usually grows in definite 

 crowded patches, in which few secondary species are found, 



