erally be obtained from druggists, wholesale druggists, or fertilizer manufacturers. Vessels of earthenware, china or glass must be used for generating the gas, since the acid employed will rapidly destroy metal and wood. An ordinary pint fruit jar will do for 12 oz. to 1 oz. of cyanid, but a narrower vessel with a bowl-shaped bottom is better, in order that the liquid (acid and water) will be deeper and better cover the cyanid when put in. A deep pint glass tumbler, a deep earthenware bowl, or a large coffee cup would also be excellent. A vessel holding only 1/2 pint is rather small for the amount of cyanid and chemicals necessary to charge a 100 cu. ft. box like previously described, since the liquid may boil over. For measuring liquids, a glass graduate, or measuring glass, having a capacity of three or four liquid ounces, graduated in fourths or eighths of an ounce, is required. A glass graduate, graduated in the metric system, may be used, and 30 cubic centimeters allowed for an ounce. Druggists should be able to supply these graduates. Suitable scales for weighing ounces and fractions of an ounce are necessary. FORMULAS SODIUM CYANID.-To fumigate citrus trees, immature peach trees, roses, buds and scions in a fumigating box, with sodium cyanid, 1/2 oz. per 100 cu. ft. space is required. The necessary amounts (liquid measure) of acid and water are respectively 12 and 3 times the amount of sodium cyanid as expressed in avoirdupois ounces. To fumigate dormant peach trees, or similar hardy deciduous trees like apple, pear and plum, with sodium cyanid, 3/4 oz. per 100 cu. ft. box space is required. The formulas for fumigating with sodium cyanid may be tabulated as follows: Citrus, etc.: 1/2 oz. sodium cyanid, 96-98% pure. 3/4 oz. sulphuric acid, 66 deg. Baume, or 93% pure. 11⁄2 oz. water. Time 30 minutes. Peach, etc.: 3/4 oz. sodium cyanid, 96-98% pure. 1 oz. sulphuric acid, 66 deg. Baume, 93% pure. 214 oz. water. Time 30 minutes. POTASSIUM CYANID.-The formulas for potassium cyanid are included for the benefit of those who may still have this cyanid on hand. Citrus, etc.: 3/5 oz.* potassium cyanid, 95-96% pure. 3/5 oz. sulphuric acid. 1-4/5 oz. water. Time 30 minutes. Peach, etc.: 1 oz. potassium cyanid. Time 30 minutes. CHARGING THE BOX Place the vessel for generating the gas, containing the necessary amount of water, in position on the earthen floor, inside the box near the middle of the front wall. This vessel may be partly buried in the earth of the floor to support it in position. After the water, add the required amount of acid. Adding the acid will heat the mixture. (Always pour the acid into the water, never the water into the acid, in order to avoid splattering of the liquids). Next suspend the required amount of cyanid, wrapped in a bit of tissue paper, in the mouth of the generating vessel (but not touching the liquid for the poisonous gas is immediately generated) by means of a string passing through the front wall at x (See illustration); or place it in the cup of the rod-and-cup device described on page 16. After placing the chemicals in readiness, place the trees to be fumigated into the box and close down the lid. See to it that the space between the walls is full of sand so that the flange on the lid will make a tight joint. Release the string, allowing the cyanid to drop into the mixture of acid and water, stopper the opening for the string and wait 30 minutes; or if the rod-and-cup device is used, simply turn the crank. Fumi *Since 2/3 or 3/4 ounce may be more conveniently weighed on most scales than 3/5 ounce, these quantities may be employed; but as the dosage is thereby slightly increased, it is advised that experimental trials of these dosages be made before regularly employing them. The proportions of potassium cyanid, acid and water are 1: 1: 3, respectively, i. e., the number of ounces of acid (liquid measure) is the same as the number of ounces of potassium cyanid (ounces avoirdupois), and the number of ounces of water (liquid measure) is three times the number of ounces of potassium cyanid (ounces avoirdupois). gate while the mixture of acid and water in the generating vessel is still warm. If the box has a small door on the side for introducing the chemicals, the trees should be placed in the box first and the lid closed down. The chemicals are then introduced through the small door: the water first, then the acid, and lastly the cyanid wrapped in a bit of tissue paper. As soon as the cyanid has been dropped into the generating jar, or vessel, rapidly close the door and fasten it into position. After 30 minutes open the lid and allow the box and contents to air for some minutes, before removing the trees. The residue in the generating vessel should be buried as it is corrosive and poisonous. MISCELLANEOUS SUGGESTIONS Trees and plants to be fumigated should have no visible moisture upon them; neither should they be packed so closely that the gas cannot circulate between them. All citrus and deciduous trees should be defoliated as required by law before fumigation, as the leaves are quite certain to be injured by the gas and will interfere with the fumigation. Ornamental citrus in tubs or pots, and ornamentals in general, not intended for sale or exchange, may be fumigated without defoliation by employing a smaller dosage, which dosage may have to be determined by trial. Those desiring more detailed information on the fumigation of many plants are referred to "Fumigation Methods," by W. G. Johnson, the Orange Judd Company, New York. CHARACTERISTICS OF CITRUS CANKER AND OF THE CAUSAL ORGANISM R. A. JEHLE A previous article* by the writer was devoted to descriptions of citrus canker and to the means of identifying it. The present paper aims to give such additional information as will enable citrus growers to attain an adequate knowledge of the disease, its nature and the respects in which it differs radically from other diseases. *The Quarterly Bulletin, Vol. I, No. 1, pp. 2-12 (1916). |