19 



systematic attention and required sustained effort. Some of these records are 

 being continued in order to secure further and more complete information upon 

 certain phases of tree behavior and additional data of some tree and fruit char- 

 acteristics. 



These investigations have revealed the occurrence and frequency of bud 

 mutations in the varieties studied, an example of which is shown in Plate 35, the 

 existence and extent of occurrence of the various strains arising from bud muta- 

 tions and their comparative commercial value, the tree and fruit characteristics 

 of the trees of these strains, and other information of fundamental importance 

 to the citrus industry. In the course of this work improved methods of propa- 

 gation have been discovered and developed, such as the use of fruit-bearing bud- 

 wood for propagation, an example of which is shown in Plate 36, instead of the 

 sucker growth which was formerly used for this purpose. Illustrations showing 

 the method of using this bud-wood in propagation are shown in Plates 37 and 38. 

 Individual tree performance records of pruned and unpruned trees of each of 

 the commercially important varieties led to the discovery of the very injurious 

 and disastrous effects of early or severe pruning (55, 58, 63) with healthy, 

 normal citrus trees. This information has resulted in the general abandonment 

 of such practices amongst citrus growers. The individual tree records, showing 

 the behavior of trees grown under different methods of soil fertilization, led to 

 the origination by the writer of an improved system of applying organic ferti- 

 lizers in citrus orchards called the furrow-manure method (53, 56, 62), which 

 has proven to be more economical and efficient than any formerly used. A study 

 of the behavior of the fruits from the lemon performance-record trees in curing 

 rooms led to the discovery of the importance of a uniform condition of atmo- 

 sphere humidity in the curing of lemons and other citrus fruits and to the inven- 

 tion of a humidifier for securing and maintaining the optimum conditions (50, 

 59). Other results might be cited, but the above are considered to be sufficient to 

 show the importance of this work. 



The results of the investigational citrus tree performance record work nat- 

 urally led to the development and use of commercial tree performance record 

 work by citrus growers for the following purposes : ( 1 ) to locate drone trees of 

 undesirable strains in the established orchards for top-working or replanting; 



(2) to locate, if possible, superior trees as sources of bud-wood for propagation; 



(3) to determine the results of cultural experiments or tree treatments; and 



(4) to carry on intelligent individual tree care in the orchards. Up to the present 

 time, 1921, commercial tree records have been kept in more than 50,000 acres of 

 citrus orchards in California and in considerable citrus acreages in southern Ala- 

 bama and in Florida. 



In commercial citrus tree records the yield of the individual trees in weight 

 or number of boxes of fruit are recorded by the foreman of the picking crew or 

 some other person at the time of picking, as shown in Plate 39. Notes are made 

 as to the production of any striking variations observed in the fruits or the trees. 

 In the investigational record work it was found that there is a definite correla- 



