390 Forestry Quarterly 



topography deal mainly with natural barriers such as large bodies 

 of water, deserts, mountain ranges, and even such vegetational 

 barriers as swamps and forests in so far as these affect dissemi- 

 nation. Ecesis consists of three important processes : germination, 

 growth, and reproduction. It is important to note that ecesis is 

 not complete unless a plant can perform all of these processes. 

 The germination of the seed depends upon its viability and the 

 nature of the new habitat. The viability depends, among other 

 things, on the character of the fruit, the seed coat, and the en- 

 dosperm. After germination the probability of its growing, 

 maturing, and reproducing depends upon hov/ nearly its own 

 physical requirements match those of its new habitat. 



Linne (32) as early as 1745 was the first to mention migration. 

 In his Philosophia Botanica (33) he gives an excellent analysis 

 of seed dissemination. Hildebrand (34) and Kerner (35) go 

 into minute detail in discussing and classifying the agents of dis- 

 tribution and the movability of seeds. De CandoUe (21) first 

 used the term barriers, and Grisebach (36) in 1872 established 

 a fundamental law of barriers. 



Succession is the phenomenon in which a series of invasions 

 occurs in the same place. It is apparent especially when the 

 natural course of events has been distributed by either physical 

 or biotic forces. In either case a series of successive invasions 

 will occur, the vegetation gradually becoming more like the origi- 

 nal until finally equilibrium is again established between the en- 

 vironment and the vegetation it supports. The ultimate or climax 

 vegetation to which all series of successions lead is the most 

 mesophytic which the area in question will support. 



Previous to 1880 we must go to writers upon forestry subjects 

 for records of observations of this phenomenon. The reason for 

 this is probably that nowhere in vegetation is succession so appar- 

 ent as in the forest. As early as 1749 succession was mentioned 

 by Biberg (37). Humboldt (38) recognized the presence of suc- 

 cession in vegetation when he stated that cryptogams prepare the 

 way for for the growth of grasses and other herbaceous plants. 

 Henfrey (39), A. de Candolle (28), Hoffman (3) and Midden- 

 dorff (5) recognized the occurrence of succession. Hoffman was 

 the first to study succession on burned-over pineries. Hult (40), 

 however, was the first to study succession in a systematic fashion. 

 He recognized the fact that most formations are merely transition 



