174 



TWENTY-EIGHTH FRUIT-GROWERS' CONVENTION. 



It is diffused in the air, in very small proportion, it is true — only about 

 four parts in ten thousand — in the form of a gas, carbon dioxid. It 

 never accumulates, though constantly given off by animal respiration 

 and decay of organic matter. 



As a correlative operation of nature, the green tissues of vegetation 

 absorb this gas and convert it into essential elements of their solid 

 structure. In the form of gas the carbon dioxid enters the epidermal 

 tissues of the leaf, a watery layer; here it becomes carbonic acid, and, 

 no longer a gas, but dissolved in water, it enters the true laboratory cells 

 of the leaf, those containing chlorophyll granules, that give the- leaves 

 their greenness. In these this raw material, drawn from the air, is 

 worked up by decomposing the carbon and oxygen and recombining in 

 marvelous ways. 



The simple experiment of putting a freshly plucked leaf into a glass of 

 water and setting it in the sunlight will aid somewhat in making visible 

 this activity of the leaf. In a little while the leaf will be covered with 

 bubbles of a gas which may be determined to be oxygen, the gas thrown 

 off in the water in the decomposition of carbon dioxid absorbed. 



If, at the same time the glass of water with the leaf is placed in the 

 sunshine, another similar one is put beneath an unpruned orange tree 

 so burdened with foliage and debris that within it is a chamber of dark- 

 ness, it will be a long wait before any like sign of leaf action will be 

 observed. 



It is well known how plants behave toward light. The colorless 

 potato plant in the cellar will grow a long way toward an opening. I 

 have just noted, while writing, a whole bunch of California poppies 

 stretching sidewise from an overhanging alder limb. Seedling orange 

 trees uniformly bear heaviest crops on the south side of an orchard, 

 though adjacent to old Navel orange trees, with interlacing roots. It is 

 quite noticeable with them, on account of the contrast of shade within 

 the orchard which their high and broad tops produce. In cool seasons, 

 in northern latitudes, budding and blossoming are most abundant on 

 the south side of trees. It was observed by many that in the back- 

 ward spring of 1902, Navel oranges set more heavily on the south side 

 of the trees. In early April of this year I noted that blossom buds 

 averaged a greater number from the axils of the outer leaf than from 

 even the next within. The botanists tell us, what is easy to note for 

 ourselves, that leaves are so arranged that one does not stand in 

 another's light. 



The absorption of the constituents of the air by the foliage eludes 

 observation, but reflection makes it reasonable that man should lend 

 his hand to favor the exposure of the leaf to the vital energies of the 

 sun's rays, and that he can profit thereby by going beyond nature's 

 efforts in the same direction. 



