26 ORANGE CULTURE IN CALIFORNIA. 



the fruit is excellent and the trees are healthy. I also have 

 an orchard on black soil, with the sub-soil near the surface. 

 Though these trees are only ten years old, and seem to be as 

 healthy as any others I have, they do not produce so good fruit 

 as is desired, despite my every effort, by good and more thor- 

 ough cultivation, to make them do so. Upon the same character 

 of soil, on a loose, gravelly sub-soil, twenty acres of trees, now 

 more than forty years old, are still in a healthy condition and 

 produce most excellent fruit. These facts must lead to practical 

 results and conclusions. They go to support my opinions, as 

 already given, and are in accordance with well-known general 

 laws. 



All my experience has reference only to the mechanical con- 

 ditions of soils on which the orange and lemon have been grown, 

 and does not convey any idea as to the chemical elements of the 

 soil, at least the quantitive elements. 



It is an established fact that trees of the deciduous order re- 

 quire at least from six to ten times more alkalies in the soils on 

 which they are grown than the evergreen varieties. It was 

 proven by analysis that one thousand parts of the dry leaves of 

 oaks yielded fifty-five parts of ashes, twenty-four parts of which 

 consisted of alkalies soluble in water. The same quantity of 

 pine leaves gave only twenty-nine parts of ashes, containing 

 four and six-tenths parts of soluble salts. 



