FRUIT-BUD FORMATION 55 



of the fruit-tree. Fats are present as reserves, but in smaller 

 quantities than the other two and are not considered further 

 in this connection. 



Nitrogen is essential in the protein sjaithesis in plants, 

 and is a necessaiy component of all protoplasmic materials. 

 This element is frequently calculated as total nitrogen in 

 analyses of plant tissues, no effort being made to separate 

 the various complexes, or it may be determined in any of its 

 various combinations. Practically all of this element is 

 derived from the soil as nitrates. Whether these are decom- 

 posed and made available for protein synthesis in the leaves 

 alone or in other tissues appears not to be entirely clear at 

 the present time. It has been widely accepted that the 

 nitrates reach the leaves through the water-conducting 

 tissues (xylem of woody plants), but recently it has been 

 argued that a major portion is transported through the 

 cortical layer (phloem).^ The relation of the nitrogen in its 

 various forms to the available carbohydrate and water sup- 

 ply seems to be of special significance in connection with 

 the differentiation of flower primordia. 



Moisture likewise is essential in the process of flower-bud 

 formation, as it is in all other phases of gro^vth. It is neces- 

 sary for digestion, conduction, transpiration, photosyn- 

 thesis, and various other synthetic processes. 



These products and materials are found in the branches, 

 trunk, and roots of the tree in somewhat vaiying amounts 

 at different times of the year. They are constantly under- 

 going change, even during much of the dormant season. 

 The cany-over effects of these materials from one season 

 or year to another are of the very greatest importance in 

 coraiection with the early growth in spring, blooming, and 

 indeed the initiation of fruit-bud development. They are 

 quite as important as the materials present in the soil about 

 1 Curtis, Otis F. Amer. Jour. Bot. 7: 101-124. March, 1920. 



