256 CHEMISTRY OF PLANT LIFE 



nutrition at the time when the " stooling " takes place. The 

 plant is thus provided with a mechanism for adapting its possi- 

 bilities of growth to the supply of growth-promoting material 

 which is available to it. 



Many other plants produce far more buds than ever develop 

 into growing tissues, and buds which, under normal conditions, 

 remain dormant, under altered conditions start into growth and so 

 provide for an " adaptation " of the total mass of the growing 

 plant to correspond with the altered conditions of growth. The 

 actual means by which certain buds are stimulated into growth 

 while others remain dormant, or are inhibited from growing, are 

 as yet unknown. Two theories have been advanced. One is that 

 the growing buds absorb all available nutrition and the others 

 remain dormant by reason of lack of growth-promoting material. 

 The other is that the vegetating (growing) tissue elaborates and 

 sends to other parts of the organism one or more substances, which 

 actually inhibit growth of the other parts, as dormant buds, etc. 

 The experimental evidence which has been presented thus far is 

 inconclusive, but seems to favor the distribution of nutritional 

 material as the governing factor, although there is some evidence 

 which seems to indicate that a supposed growth-inhibiting sub- 

 stance is actually translocated from rapidly-vegetating tissues 

 to other parts of the plant. There is, however, no explanation 

 of how the buds, or other tissues, which do grow get their initial 

 stimulus, while the dormant buds do not. After growth has once 

 started, the changes in osmotic pressure due to the accumulation 

 and translocation of synthetized materials can account for the 

 movement of new nutritional material for the synthetic processes 

 into the growing organ; but this would not account for the selective 

 stimulation of only a part of the buds, or possible growing points, 

 of a plant, or for an adaptational development of others under 

 altered conditions of growth. 



The form of morphological adaptation which has been dis- 

 covered in the course of the study of the native vegetation of the 

 campos of Brazil (which have a very dry season and have been 

 regularly burned over by the natives for many generations) in 

 which the papilionaceous shrubs have developed underground 

 trunks, or stems, and seem actually to profit in luxuriance of 

 growth when the rainy season comes on by reason of this mor- 

 phological adaptation to the unusual environmental conditions, 



