Plant Qrowth'Suhstances 



plant growth as it would be to confuse vitamins with hormones 

 in speaking of animal physiology. 



Link et al. (1937, H) have proposed a complicated nomen- 

 clature for all growth substances. 



Their "autoauxone" is apparently an unnecessary synonym 

 of "hormone" {sensu stricto sive plantar um sive animalium) . A 

 hormone is excellently characterized by the phrase of Link et 

 al. : "produced by the individual whose development it 

 affects." "Auxone" is much the same as Bottomley's "auxi- 

 mone", and not obviously preferable thereto. The additional 

 term "heteroauxone" (or possibly "heterauximone") brings to 

 the nomenclature a little more definition than does "auxim- 

 one" alone, but only if "auximone" is used in the most 

 general sense to mean any accessory substance (not an 

 ordinary nutrient) affecting growth and cell-differentiation. 

 It appears that historical and linguistic propriety would be 

 satisfied if the term "hormone" were reserved in its usual 

 sense, and "auximone" (or "phytamin") were used for 

 substances affecting growth of an individual not producing 

 them. 



Link et al. have performed a useful service in pointing 

 out the need for distinguishing between different modes of 

 tissue growth, but the necessary distinction can be made with- 

 out resort to ponderous words to designate the incitants of 

 such growth-modes. 



An unexceptionable definition of a hormone is that given 

 by Went and Thimann in their book (mentioned on p. 23). 

 It is: 



"A hormone is a substance which, being produced in any 

 one part of the organism, is transferred to another part and 

 there influences a specific physiological process." 



This covers both animal and plant hormones. If it is 

 desired to distinguish hormones of plants from those of 

 animals, the former may be called phytohormones. This term 

 is widely known, though comparatively seldom used in its 

 proper sense ; it is often used to connote a synthetic growth- 

 substance, i.e.y a drug applied from outside. The acceptance of 



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