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THE AMERICAN NATURALIST. [Vol. XXXVIII. 



resin cysts in Sequoia, Abies and Tsuga, which Jeffrey appears 

 disposed to formulate as a general law, it is not clear to us how 

 this can be made to harmonize with facts coming under our own 

 observation. It has been shown that such resin cysts occur in 

 one species of Sequoia, four species of Abies and one species of 

 Tsuga, yet another species of which also shows them in a poten- 

 tial form. The same elements appear in each case, viz. : — 



1. The cysts assume a definite form in distribution. 



2. They always occupy a definite place in the scale of struc- 

 tural organization. 



3. They are constant features of the same species'. 



4. They occur at frequent intervals in the same transverse 

 section, showing them to be repeated at intervals of from one to 

 several years. 



It is exceedingly difficult to conceive how injuries could be 

 inflicted upon particular species with such constancy, and in 

 1 to produce uniform results in the production of 



resm cysts which occupy a definite place in the structural scale. 



It is a well known fact in the physiology of plants, that con- 

 ditions which induce a premature development of parts also 

 bring about the conversion of potentialities into actuahties, and 

 under such circumstances the latter become evidences of a 

 pathological condition. The swamp maple normally develops a 

 brilliant foliage in the autumn but it is not uncommon to find 

 individual branches which have been injured, or even entire 

 trees, which exhibit the characteristic autumnal foliage in mid- 

 summer, a condition which is con-ectly interpreted as pathologi- 

 cal. Special conditions of nutrition, e.g., an excess of mineral 

 food elements, may similarly induce a premature development 

 of the reproductive process. It has been shown by Richards 

 that in cases of injury the rate of respiration is greatly in- 

 creased, an alteration in functional activity which he rightly 

 interprets as due to efforts directed toward the repair of injured 

 parts. But this implies a local increase of nutritive materials 

 and their application to a more intensive process of nutrition. 

 Such features are well known in the case of all hypertrophies, 

 and they must be similarly applicable to all forms of wounds, no 

 matter what their origin, differing only in degree. We cannot 



