164 PLANT PHYSIOLOGY 



extract from yeast and that from truffles (which are also Ascomy- 

 cetes) but not from the ordinary mushroom (which is a Basidiomy- 

 cete). In the seed plants, injections from different regions — root, 

 stem, or leaf — cause the same precipitin reactions. This work has 

 thus opened a whole new field in the determination of plant and 

 animal relationships. It is interesting to note in this connection 

 that legumes which cross-inoculate with the same bacteria (Chap. 

 IX) have the same type of proteins. 



If a small amount of a protein (the sensitizing dose) is injected 

 into the blood of an animal and then some days later (7 to 30, 

 depending upon the size of the sensitizing dose) another injection 

 is made of the same protein (the intoxicating dose), the animal 

 may undergo a severe shock and even die within a few minutes. 

 This anaphylactic shock may be brought about when the sensitizing 

 dose is as small as 0.00000005 g. of protein (egg white) and is 

 another indication of the high specificity of proteins. Hay fever is 

 now considered to be a case of anaphylaxis, in which the patient 

 has become sensitized to some individual protein, generally pollen. 

 This anaphylactic reaction has been reported in plants by Lumiere 

 and Coutourier, who sensitized leaves and bulbs to horse serum, 

 using 0.01-0.02 c. c. After three weeks 0.2-0.3 c. c. were given to 

 both the sensitized organs and to controls; four days later those 

 that had been sensitized began to wither and die, while the others 

 remained normal. 



About twenty-five different amino acids have been isolated from 

 proteins, some of which have been found free in plant tissues, 

 particularly in germinating seeds and in rapidly developing buds 

 and shoots, where proteins are undoubtedly undergoing changes. 

 Under these conditions the amino acids are found as transition 

 products in the synthesis or decomposition of proteins. Among 

 the common amino acids are leucine, lysine, arginine, tyrosine, 

 proline, histidine, and tryptophane. (The name of an amino acid 

 generally ends in ine.) Different amino acids seem to be con- 

 nected with different physiological activities in the animal organ- 

 ism. Tryptophane, while essential to the maintenance of life, 

 does not promote growth. Lysine, on the contrary, definitely 

 favors growth. Arginine is associated with reproduction, and cyst- 

 ine with the production of hair, feathers, etc. Such correlations 

 between the amino acids and physiological activities have not yet 

 been noted for plants. 



