A Canadian correspondent informs me that he, with others, has been very successful in growing mushrooms in the open air during the summer months in Canada, and gives the following directions for preparing the beds in the colder latitudes:

Place under a shed such amount of clean stable manure as may be required for the beds, turning it over and over until all free ammonia has escaped and the tendency of undue fermentation and evolution of high temperature has greatly modified. To effect this, it is necessary to heap up the manure each time in a mound, say three feet high after turning, and beat it firmly down (the exclusion of free air prevents overheating). To put the manure in proper condition for use in the beds, from two to four weeks' treatment may be required, but much depends on the quality of the manure and temperature of the atmosphere. Before making the beds, and several days after the last turning, test the internal temperature of the mound in the following manner: Make a hole with a broomstick through the mound from top to bottom, and suspend a thermometer half way down in the hole for, say, an hour. The temperature may be as high as 150° F. After the lapse of the time stated, beat the mound more firmly down to prevent rise of temperature. Test again two days after in the same manner. If the temperature has risen several degrees the mound must be again taken down, turned over, and remade. If, on the other hand, the temperature has fallen to 100° F., the permanent bed may be made. If indoor growth is desired, such as a cellar, outbuilding, or cave, the atmosphere must not fall below 50° F., nor be over 80° F. Air drafts cannot be permitted. The floor must be dry and the atmosphere moist. The cellar may be dark, or moderately light. Growers differ in opinion in this respect. Growers generally add to the manure about one-fourth or one-fifth garden soil, but success has been attained without the use of garden soil, except as surface dressing after spawning the bed; an excessive use of loam, in any case, tends to lower the temperature too rapidly. Having prepared a box or frame-work for the bed twelve inches deep, fill it up to within two inches of the top; beat gently down with a board, or a brick, until it is even and compact. On the following day make holes in the bed, with a dibble, ten inches deep, in which suspend a thermometer half way down for an hour. Should the temperature have fallen to 90° F., cover lightly with straw and test on the following day. Should the temperature prove to be going down, say to 80° F., or 85° F., it is safe to plant the spawn; but should the temperature be on the rise, wait until it is falling. One grower has stated that his greatest success has been when the spawn was planted at the temperature of 75° F. Should the temperature fall too quickly and the surface be too dry, sprinkle with water at blood heat, using a very fine hose, and cover the bed with straw.

The spawn brick should be cut into pieces, about the size of an egg, and planted in holes made in the bed, about two inches deep and about six inches apart. The holes are then filled up and about two inches of garden soil sifted over the surface of the bed. Tamp the bed surface gently with the back of a spade. Mushrooms may be expected for table use in about six or seven weeks, provided the spawn is good and the temperature has not fallen below 50° F. In outdoor culture the beds must be well covered with straw or canvas, and had better be under a shed roof with southern exposure.

The spawn used by this grower is the "brick" spawn, imported from Carter & Holborn, London, England.