THE SPRING FLORA 195 



b. List the dominant species of each association and indi- 



cate whether they are annuals, perennials, biennials, 

 rnesophytes, xerophytes, or hydrophytes. 



c. Discuss the relation of the habitat of each association 



observed to the habit of the species comprising the 

 association. 



d. Explain any discrepancy found between the habitat and 



the habit of plants in the shore associations studied. 

 4. Origin of new associations. 



a. Shore-line associations. Do you find indications of migra- 



tion, invasion, and succession in the shore-line associa- 

 tions ? Are plants invading the mud or gravel of the 

 immediate shore zone ? If so, what kinds of plants 

 are they, and from what place did they come ? Are 

 they species with special devices for dissemination ? 

 Are they found in the adjacent associations or are 

 they migrants from distant locations ? Have they 

 any special adaptations for their new habitat ? Do 

 you see any evidence of succession, or the replace- 

 ment of one association by another ? Discuss in your 

 notes the phenomena observed. 



b. Denuded areas. Select an area from which the vegetation 



has been removed within a comparatively short period, 

 as on a denuded bank, field, garden, or roadside. 



(1) What plants are invading the area ? Are they from 



the adjacent vegetation ? "What are the means 

 by which these species originally migrated to the 

 new home ? Have they special adaptations for 

 becoming established in the new habitat? Is 

 there a definite relation between the habitat and 

 the habit of the invading species ? 



(2) Discuss the above facts concerning the area being 



investigated. 



