242 CHEMISTRY OF PLANT LIFE 



and so make it more easily penetrable by the hyphae of the par- 

 asite. 



It will be seen that, in general, " hormones " are a type of 

 substances (possibly often present in plants in the form of glu- 

 cosides) which are supposed to stimulate the degenerative (or 

 katabolic) vital processes in contrast to the synthetic (or anabolic) 

 changes. It has been suggested that they do this in either one of 

 two ways; namely, by favoring the introduction of water into the 

 protoplasm and so diluting the cell contents, changing the osmotic 

 pressure, etc.; or by bringing about a separation of the colloidal 

 layers, or films, of the protoplasmic complex, producing a result 

 similar to that produced by freezing the tissues. These ideas 

 have been suggested by studies of the changes in the protoplasmic 

 equilibrium of protoplasm when foreign substances are introduced 

 into it. These studies have not as yet been brought to the stage 

 of final conclusions, and the ideas presented must be considered 

 as suggestive rather than as conclusive. 



VITAMINES 



" Vitamines," as contrasted with " hormones," are supposed 

 stimulants of synthetic metabolic processes, or accelerators of 

 growth, rather than of degenerative processes. 



The term " vitamine " was first used to designate the sub- 

 stance, or substances, which must be present in the diet of animals 

 in order that the animal organism may grow. Absence of these 

 substances from the food of the animal results in the stoppage 

 of growth of young animals and in various so-called " deficiency 

 diseases " (such as beri-beri, scurvy, polyneuritis, etc.) of adults. 

 This means that the animal organism is altogether unable to elab- 

 orate its own vitamines, and extended investigations have indi- 

 cated that the vitamines necessary for animal uses are wholly of 

 plant origin. The name " vitamine " was first used because it 

 was supposed that these substances are chemical compounds of the 

 amine type and, since they are necessary to normal life processes 

 of animals, the name " vitamine " seemed to represent both their 

 chemical character and their functions. Later investigations 

 have caused, doubt as to the accuracy of the first belief as to their 

 chemical nature, and various other names have been suggested 

 for the general group of substances which have the observed bene- 



