268 IOWA ACADEMY OF SCIENCE Vol. XXV, 191S 



of the sap due to the evaporation of the water through dry 

 weather; and third, that, since every bud of the apple tree is a 

 l)otential tiower bud, the weather must liave much to do in det^r- 

 Miininj^ the number of flowere formed. 



Drinkard (8), in 1909 to 1910, working- in Virginia, studied 

 in detail the development of the tiower biuls of three varietie^s 

 of apples. He notes the foUowino' facts concerning tlie Olden- 

 burg (l)uchevss) apj)le. The date, of leaf and flower bud dif- 

 ferentiation was as early a.s June 20. This wa.s innnediately 

 followed I)y a period of active growth in which all floral organs 

 except the pistil were formed l)y Juh' 7 and all of the flower 

 parts were f owned by the first of November. In the following 

 spring pollen grains were completely formed and the flowers 

 were ready to open by April first. In conclusion the following 

 statement is made: "The proper development of the fruit bud 

 would therefore be influenced by factors whieli are brought to 

 bear upon the tree prior to and during the period at which 

 fruitobiid formation takes place. In the practice of such or- 

 chard operations as are designed to influence or control fruit-bud 

 formation, it appears that such operations should be mere effec- 

 tive in the spring and early summer thai at other stuge-s of 

 development." 



The truth of the last statement was verified by later experi- 

 ments. In 1913 and 1915 Drinkard (9) conducted experiments 

 to determine the effects of pruning, ringing, and stripping on 

 the formation of fruit buds on the dwarf tpple trees. The 

 results indicated that s])ring pruning at the time of the resump- 

 tion of growth retards the formation of fruit buds, while smn- 

 mer pruning the last of June greatly stimulated the formation 

 of fruit buds. Fall pnining in November had little effect on 

 bud formation. Stripping in June acted the same as pruning 

 at that time. Ringing also stimulated bud formation Avhen done 

 after the leaves matured. 



Remy (29) in 1911 stndied relations existing ])etween the f<.'r- 

 tilizers applied to the soil ami the amount of nutritive sub.stance> 

 in the various oi'gans of the tree. One row of trees received a 

 fertilizer containing all of the necessary elements while in the 

 other rows nitrogen, potash, phosplioric acid, and lime, rcvspect- 

 ively, were wathheld. 



It was observed that a certain amount of nitrogen is necessary 

 for the abundant development of fruit buds and that the ratios 



