170 CLASSIFICATION OF SERES. 



nized that a secondary sere may occasionally resemble a primary one very closely 

 upon casual inspection. In rare cases, they can be distinguished only by the 

 fact that the prisere has the pioneer stage, while the subsere begins with a 

 late initial or subpioneer stage. Such instances are very rare, however, and 

 in the vast majority of cases a subsere begins with a medial or subfinal stage. 

 This occasional approximation of prisere and subsere is not an argument 

 against the validity of the concept. In the individual plant an exact parallel 

 is found in the case of species which replace the reproductive seeds wholly or in 

 part by propagative bulbils, the development of the individual being all but 

 identical in the two cases. 



Cowles (1911 : 167) states that the classification into primary and secondary 

 successions "seems not to be of fundamental value, since it separates such 

 closely related phenomena as those of erosion and deposit, and places together 

 such unlike things as hmnan agencies and the subsidence of land." This 

 objection brings out clearly the difference between the physiographic and the 

 developmental views of vegetation. The former apparently makes physio- 

 graphic distinctions paramount, while the latter regards development as the 

 sole arbiter of the importance or value of any concept or prinicple. It has 

 repeatedly been shown (Chapter II) that, while erosion and deposit are 

 closely related physiographic processes, they are not closely related successional 

 phenomena^ Successionally they are indeed usually antagonistic, giving rise 

 to fundamentally different bare areas. On the other hand, they may occa- 

 sionally be equivalent as initial causes, producing xerophytic sand areas at 

 one extreme or hydrophytic swamp areas at the other. In the life-history of 

 a river the erosion of upland is obviously related to deposition in lowland, 

 since the material for the one comes from the other. It is clear that no such 

 relation exists between the two areas in so far as succession is concerned. 

 Erosion on the upland yields regularly a xerarch sere, deposition on the low- 

 land a hydrarch sere. The two seres may show a developmental relation by 

 terminating in the same climax, or they may belong to wholly different forma- 

 tions. In either case, it is evident that the student of development is con- 

 cerned wtih erosion and deposit only because, like a host of other agents, they 

 produce initial bare areas for invasion. 



Furrer (1914 : 30) has criticized the distinction into primary and secondary 

 succession as a "far-reaching division, based predominantly upon deductive 

 reasoning, and supported by insufficient analysis derived from practical 

 experience." He further regards it as questionable whether the field ecofogist 

 can ever fall in line with this clasisfication. This objection seems immaterial 

 in view of what has been said in the preceding paragraph. Moreover, Furrer's 

 experience in successional investigation is so very slight that little weight can 

 be given his opinion of a developmental relation which has had more rigorous 

 and extensive field tests than any other developmental concept except suc- 

 cession itself. 



Roberts (1914 : 432) concludes that: 



' ' The terms initial and repetitive seem to be better than primary and second- 

 ary in conveying the idea of often-repeated successions such as are foimd in a 

 frequently deforested area. (443) 



" It is doubtful if there is any climax representing that of the so-called primary 

 succession, which might well be called the initial succession. The region 



