CHAPTER XIII 



DECAY: ITS MODE OF ACTION AND EFFECTS 



In discussing the operation of decay in the woody tissue of 

 a stem, it will be desirable to have reference to (i) the nature 

 of the active agents, (2) the conditions under which they flour- 

 ish, (3) their mode of operation, and (4) their effects upon the 

 structure and mode of preservation. 



i. The nature of the active agents. Decay has its origin in the 

 growth of certain plants of a low degree of organization, which, 

 through their ability to seek food supplies either in living or 

 dead organic bodies, produce such an unusual course of develop- 

 ment as to effect an actual disorganization of the tissues, as 

 expressed in decay. To understand fully the nature and mode 

 of operation of these plants, it will be necessary to briefly pass 

 in review their essential characteristics. 



Among the lower forms of plants we recognize two somewhat 

 nearly related groups, which present many features in common, 

 both with respect to their influence upon the promotion of dis- 

 ease and decay and to their general habits of life, but which 

 nevertheless differ very materially in their structure and the 

 details of their life history. The first group embraces what are 

 known as the Bacteria, - - plants characterized by their unicel- 

 lular structure, which rarely assumes a filamentous form, and 

 by the fact that while they may and frequently do propagate 

 through the medium of spores, they more commonly multiply 

 by simple fission, in consequence of which they are designated 

 the fission fungi or Schizomycetes . Their life history is very 

 simple, and the incomplete cycle, which is wholly devoid of a 

 sexual phase, is repeated at very frequent intervals, so that they 

 multiply with enormous rapidity. The nutrition of the bacteria 

 is derived by a process of direct absorption from the surrounding 



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