Nomenclature 



for example, is like an unpleasant telegram, a hormone can be 

 likened to a key, a bundle of manuscripts, or a sample of 

 merchandise — that is, something passing between two parties 

 and essential to the carrying out of a transaction. 



Note, however, that Bayliss's hormone, and the many 

 others discovered since, all pass between two parts of the same 

 body. A medicine or a poison administered from without may 

 produce a very marked result on the body, but it is not there- 

 fore a hormone. Vitamins are not hormones, because they 

 have to be supplied to the human or animal body from a 

 plant source — that is, from outside. 



Phenyl-acetic acid or its more powerful relatives, such as 

 indolyl-acetic acid, produce remarkable effects on plants, 

 particularly by way of initiating adventitious root-growth. 

 They are, however, more like vitamins than they are like 

 animal hormones, and it would be fair to call them vitamins- 

 for-plants. In any case, it would be misleading to continue 

 to call them hormones, unless it can be proved that they are 

 formed within the plant and act as natural chemical messen- 

 gers within it. 



There can be no objection to an extension of the meaning 

 of the word "hormone" to connote substances so acting in 

 plants. There is a small class of growth-substances, which do 

 occur in plants and do regulate growth within them. Vitamin 

 C is produced in the plant and regulates some growth- 

 processes within it (von Hausen, 1936). On the basis of von 

 Hansen's work, vitamin C is a type of true plant-hormone, 

 in which class come also the two auxins, the plant female 

 hormone of Butenandt, and possibly a male hormone. On 

 the other hand, such products as those of decomposition and 

 of putrefaction, whether derived from processes taking place 

 in the animal gut or in the compost heap, or derived from 

 synthetic processes, are supplied externally to the plant and 

 cannot be called hormones : they are auximones, or vitamins- 

 for-plants. Unless it can be proved that the "synthetic" 

 growth-substances occur naturally in plants, and regulate 

 growth within them, it would to-day be as absurd to give the 

 name "hormone" to these exterior substances which affect 



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