Rev. P. Keith on the Structure of Living Fabrics. 1 1 



will run thus: All animals have tails. Cows have tails, horses 

 have tails, asses have tails ; ergo, frogs have tails also. Your 

 antagonist may indeed say, Oh, but I have examined a frog, 

 and I cannot see its tail. But your reply will be, — It is of 

 no consequence that it has not a visible tail ; it has a poten- 

 tial tail, and that is enough. — Such is the advantage of the 

 argument from potentiality. 



Yet Mr. Burnett admits in his own creed, what he con- 

 demns in the creed of others. Speaking of animals, he says, 

 " Nutrition may be performed without a mouth to receive, 

 teeth to chew, or even a stomach to digest, the food ; respira- 

 tion without either lungs or gills; prehension without either 

 hands or claws ; and progression without either wings or feet." 

 What is this, but to admit that certain animals are destitute 

 of these organs? and what is the describer to say? or the 

 arranger to do? — Oh, says Mr. Burnett, found your divisions 

 upon special functions, and not upon special organs : divide 

 the several parts of the plant into nutrients and generants, and 

 then you are sure to be right ; for whatever is not a generant 

 is a nutrient, and whatever is not a nutrient is a generant. 

 To be sure there is in vegetables a certain tertium quid, a 

 thing called a stock or caudex, " an accessory or interme- 

 diate, — the organ of extension, formed more or less of both 

 extremes, and serving equally for their varied segregation and 

 extension, " which there is some little difficulty in disposing 

 of; and yet after all it may belong either to the one or to the 

 other, and be disposed of accordingly. But with all due de- 

 ference to Mr. Burnett and his opinions, we may safely affirm 

 that the division into nutrients and generants will leave him 

 just where he was before. If he is describing any particular 

 plant, he must tell us of what organs its nutrient system con- 

 sists. Has it a root? has it a branch? has it a leaf? He must 

 do the same thing by the generant system also. Has it a 

 flower? has it a seed? has it a seed-vessel? — And after all, 

 there is nothing novel in the matter. The division here re- 

 commended has been long recognized by physiologists, and 

 even introduced into their arrangements. If Mr. Burnett will 

 take the trouble to look into Keith's System of Physiological 

 Botany, published in 1816, he will find that the structure of 

 the plant is exhibited upon the express ground of such a di- 

 vision ; namely, upon that of conservative organs and repro- 

 ductive organs, — the former corresponding to Mr. Burnett's 

 nutrients, and the latter to his generants; and the method 

 followed up throughout the whole extent of the vegetable king- 

 dom, as distributed into Perfect and Imperfect plants, the 

 Perfect plants being regarded as comprising the Phamogamia 



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