ECOLOGICAL CLASSES 175 



as possible for the prevalence of the latter. State what would prob- 

 ably be the condition of the piece of ground examined if left unmo- 

 lested for ten years or more. 

 Kkfekences. Clements, 59 ; Principles, Chapters XXXIV, XXXV. 



PLANT SUCCESSIONS 



156. Field study of successions. 



A. p:xamine a field of wheat, rye, oats, or barley, when the grain is not 

 more than a foot high, again when it is ready for reaping, and finally 

 as long as possible after reaping, before fall plowing or frost destroys 

 the plants upon it. Make a list of all the plants that can be recog- 

 nized at each period, and note which ones are in blossom or in frait. 



B. Study wood lots with full-grown trees upon them, others from which 

 the trees have recently been cut off, others still which have been 

 cleared for many years. Make a general statement of the kinds and 

 relative numbers of seed plants of all sorts found in each case. 



C. If possible, study the changes in the vegetation of old fields allowed 

 to grow up to weeds and bushes. 



Draw up a general account of what you have found to be the order 

 of succession of plants in grain fields, in cleared woodland, and in 

 abandoned fields. Try to give some reasons why the plants succeed 

 one another in the order actually observed. 

 liKFERENCES. Clcments, 59; Schimper-Fisher, 56; Warming-Groom- 

 Balfour, 57 ; Principles, Chapter XXXV. 



ECOLOGICAL CLASSES 



157. Field study of ecological classes.** 



A. Examine the vegetation of any accessible lake, pond, marsh, 

 or river, of ordinary woods, thickets, and grass lands, and 

 of the driest areas in the region, such as sand hills or dunes, 

 barren knolls or banks, ledges or outlying masses of rook. 

 Select some of the typical inhabitants of each region and 

 make a list of : 



,. „ , , ( (ct) living only in water. 



(1) Hydrophytes^ ^ \. . . / . , • ^ •, 

 ^ ^ -^ ^ -^ [(^>) hvmg either in water or in very wet sou 



(2) Mesophytes. 



(3) Xerophytes. 



