94 STUDIES IN THE VEGETATION OP THE STATE 



species occurring only occasionally in the formation. Aster 

 levis and A . azureus are woodland elements growing in prai- 

 ries and meadows adjacent to woody formations. These two 

 woodland asters occur sparsely to subcopiously in thirteen 

 out of twenty-seven quadrats representing important physi- 

 ographical variations. In other meadows, I have counted 

 400 individuals of each of these species in one quadrat. The 

 numerous light blue flower heads appear about the middle of 

 September and stand in marked contrast with the withering 

 facies. Both species are pleiocyclic, and rosette formers, 

 v.'ith generally several stems proceeding from the same peren- 

 nial root. Ambrosia trifida is a robust annual forming her- 

 baceous thickets in dravi^s, ditches, and along roadsides. The 

 great ragweed is one of the worst roadside ruderals, since it 

 adapts itself to almost all conditions, though preferring 

 rather moist land. Its diclinic, anemophilous flowers produce 

 copious, powdery pollen masses which are protected by the 

 inverted saucer-shaped involucres. Carduus altissiinus is a 

 tall, branched thicket and woodland species occurring rarely 

 in the wet meadow; it is a pleiocyclic herb and forms closed 

 rosettes. Helianthus annuus is prominent on account of its 

 extreme size by virtue of which it often becomes controlling 

 in the floral covering. Its distribution has been indicated 

 heretofore. The Jerusalem artichoke, Helianthus tuberosus, 

 and the horsemint, Monarda fistiilosa, grow in thickets of 

 Corylus within the prairie, and also along the creek. Both are 

 pleiocyclic woodland species, perennial by rootstalks, the 

 former also with tubers and fleshy rootstalks. Muhlenhergia 

 racemosa, a frequenter of banks of streams and edges of wood- 

 lands, grows rather commonly in the low meadows. It is 

 also perennial by means of rootstalks. Acahfpha virginica 

 is a small annual of deep woodlands found at a few stations in 

 the low meadows where it forms patches of rather robust in- 

 dividuals; it is not abundant enough, however, to be of im- 

 portance in the formation. Guscuta paradoxa forms an in- 

 terrupted layer in the sunflower patches on the east of the 



