170 MISSOURI BOTANICAL GARDEN. 



season of this plant may be interrupted, tlie interruption some- 

 times lasting a month or more. This was especially to be 

 noticed during the spring of 1907, in which year the unusu- 

 ally warm weather during February and March, followed by 

 a cold period with killing frosts, brought about a second 

 flowering period of Claytonia virginica during May, 



In the early summer an occasional specimen of Anemone 

 caroliniana, very rare on the Missouri side of the section studied, 

 is met with. Not abundant is Aralia quinqiiejolia. RaniiU' 

 ciihis fasciculans is not Infrequent. The principal sedges 

 and grasses are several species of CarcXy especially C. 

 laxijlora latijolia^ Alelica diffusa and Muhlenbergia diffusa. 

 In drier places Hypoxis ereda is frequent. 



During the fall the Compositac give the tone to the whole, 

 principally Eupatorium ageratoides and E. altissimum, Rud- 

 beckia triloba ^ Solidago ulmifolia, Verbesina helianthoides and 

 Vernonia noveboracensis, though Pycnanthemum linifolium 



is frequent. 



Ravines. 



such 



the river combine with their typical mesophytic flora not a 

 few of the xerophytes w^hich have wandered in from the 

 adjoining bluffs, as well as the hydroi)hytic flora derived 

 from springs and hillside creeks, thus forming a very strik- 

 ing modification of the deciduous oak forest. Owing to 

 the underground drainage, only moisture-loving oaks such as 

 Querciis alba, Q. cocdnca tinctoria. Q. macrocarpaj Q. Muhlen- 



Q 



with Sassafras offi 



Acer saecharinumj Juglans cinerea, J. nigra, Carya amara and 

 C. olivaeformis, are the principal trees. The smaller trees 

 and shrubs as a rule never form thickets but are sohtary 

 or subsohtar}^ These are Admina triloba, Ceanothus ameri- 

 caniis, Cerds canadensis^ Hydrangea arborescens, Viburnum 

 rufotomeiitosum and Lindera Benzoin. 



Herbaceous growth is well represented throughout the 

 seasons. In spring the Ranunculaceae arc numerous, the 

 pi'Incipal species being Actaea alba, Anemone virginiana, 

 Ranunculus abortivus, R. recurvatus, R. repens and R. scp- 



tentrionalis . 



f 



