82 



TPIIRTY-FOURTH FRUIT-GROWERS CONVENTION. 



In connection with the effect of natural conditions, such as tempera- 

 ture, moisture, food elements, etc., upon the growth of plants, two 

 peculiarities of the citrus tree may be mentioned here. The first relates 

 to its manner of growth. ^lost of our ordinary fruit trees are 

 deciduous. Their life each year is marked by a period of growth during 

 the summer and a period of rest during the winter. In their woody 

 stems and branches the substance formed each year takes the form of 

 an annual ring, the number of which corresponds very closely to the 

 age of the tree. These rings are visible on account of a difference in 

 the structure of the wood formed in the spring and during the summer. 

 At the beginning of each growing season, large amounts of sap circulate 

 in the tree, and the first wood which forms at this time ha»s a very coarse, 

 porous structure, being composed of comparatively large open vessels, 

 which are mechanically adapted to conducting the large amounts of 

 sap which are flowing at this time. As the season advances the woody 

 growth in thickness becomes less, the amount of sap diminishes, and 

 the wood, now formed has a closer, denser structure with much smaller 

 vessels, until finally, toward the end of the summer, growth ceases 

 altogether. The next spring another porous coarse layer is formed 

 outside the fine-grained wood of the previous fall, and from this differ- 

 ence in structure the annual rings are visible to the eye. The difference 

 is also of importance, as just pointed out, from physiological reasons, 

 the coarse-grained spring wood allowing the passage of the large 

 amounts of sap which are flowing in the tree at that season. 



In the citrus tree a number, of growths take place each year. Each 

 of these is marked by a definite ring of wood in the stem and branches, 

 so that if the tree makes five growths during the season, five j-ings 

 .vnll be found in the wood for that year. The fact pointed out above, 

 that the structure of the wood is of great importance as permitting 

 or obstructing the flow of sap, is the vital one in this connection. 

 Citrus growth, while having a certain normal regularity under uniform 

 conditions, responds in a very marked degree to the treatment which is 

 given the tree, particularly that in respect to moisture. Growth 

 naturally follows an abundant water supply and vice versa. If, then, 

 the water supply should be extremely irregular, disastrous results may 

 follow from this peculiarity in the growth of the tree. During a 

 period of dryness, the woodj^ tissue which serves as a channel for 

 conducting the sap becomes dense, fine-grained, and of poor conducting 

 quality. If the tree is then suddenly supplied with a large amount 

 of water, its trunk and branches are not able to conduct that which is 

 sent up from the roots, and complications may result. Further than 

 this, the citrus tree is one in which the flow of sap from the roots is 

 extremely free and abundant. One needs but to cut off the top of a 

 vigorous orange or lemon tree, and then supply the root abundantly 

 with water, to discover the remarkable freedom and promptness ■ with 

 which the excessive amount of water is sent up by the root into the 

 trunk. 



The second peculiarity of the citrus tree alluded to above is one 

 which it shares with the cherry, peach, apricot, and other stone fruits, 

 and a few other plants. This is a tendency to form and exude masses 

 of a gummy substance as the result of injury, or even from unfavorable 

 natural conditions. The gumming is due to complicated physiological 



