THE INFLUENCE OF CERTAIN DUCTLESS GLAND 

 SUBSTANCES ON THE GROWTH OF PLANT 



TISSUES. 1 



ROBERT A. BUDINGTON. 



That thyroid gland constituents and secretions contain sub- 

 stances which effect clear, and often far-reaching, influences on 

 the metabolism and action of animal cells has long been recog- 

 nized, both from observations of natural wild stock, and from 

 experimental data. As a normally produced hormone, or as a 

 substance introduced artificially, thyroid substances alter the 

 norm of the metabolism of an adult tissue; in no less, but rather 

 in more pronounced ways, thyroid tissue fed to growing embryos 

 modifies their growth and differentiation. 



Proof of the above has been furnished by numerous workers 

 for vertebrates, especially for representatives of the mammalia 

 and amphibia; and for insects and insect larvae, as Northrop 

 and Kunkel, respectively, have demonstrated. Protozoa also 

 show a marked modification of their metabolic processes when 

 they feed upon or absorb thyroid gland products, as indicated by 

 the work of Nowikoff, Shumway, Budington and Harvey, and 

 more recently by Chambers. 



After noting that living substances in organisms of such widely 

 different constitution and phylogenetic position seem distinctly 

 susceptible to this hormonic material, the question arises, Is 

 thyroid substance a compound with special potencies over animal 

 metabolism, or is all protoplasm amenable to its influence? 

 Assuming a single origin of living material, has the wide di- 

 vergence of the animal and plant kingdoms produced in the 

 latter a type of protoplasm which may be immune to this glandu- 

 lar product, so foreign to plants in its place of synthesis? 



This paper reports the morphological effects of thyroid con- 

 stituents on the growth of the root-tips of the onion, Allium. 

 To avoid seasonal eccentricities, the experiments were repeated 



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1 From the Department of Zoology, Oberlin College. 



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