"4. Horse dung one part, cow dung two parts, sheep's dung one part.
"5. Horse droppings from the roads one part, cow dung two parts, mixed with a little loam.
"6. Horse dung, cow dung, and loam, in equal parts."
From the above it appears that horse dung and cow dung are the principals in spawn bricks; the loam is added for the purpose of making the other materials hold together; it also absorbs the ammonia, which otherwise would pass off.
J. Burton's Method. From The Kitchen and Market Garden.—Make the spawn in early spring. As cow manure is the principal ingredient used in making the bricks this should be secured before the animals get any green food. Store it on the floor of an open, dry, airy shed, and turn it every few days for a week or two. Then add an equal part of the following: Fresh horse droppings, a little loam, and chopped straw, mixed together. "The whole should then be worked well together and then trodden down, after which it may be allowed to remain for a few days, when it will be required to be turned two or three times a week. If the weather be fine and dry the mass will soon be in a fit condition for molding into bricks, which process can be performed by using a mold in the same way as the brick makers, or, ... the manure may be spread evenly on the floor to a thickness of six inches, and then be firmly trodden and beaten down evenly with the back of the spade. It should then be lined out to the required size of the bricks, and be cut with a sharp spade or turfing iron. In a few days the bricks will be sufficiently dry to handle, when they should be set up edgeways to dry thoroughly, and if exposed to the sun for two or three days they will be ready to receive the spawn. In introducing the spawn two holes large enough to admit a piece of spawn as big as a pigeon's egg should be cut in each brick at equal distances. This should be well beaten in and the surface made even with a little manure. The bricks should then be collected together in a heap and covered with enough short manure to cause a gentle heat, being careful that there is no rank heat or steam to kill the spawn. This must be carefully attended to until the spawn is found to have penetrated through the whole of the bricks, after which they should be stacked away in any convenient dry place."
HOW TO MAKE FRENCH (flake) SPAWN.
I can not do better than to let a practical Frenchman engaged in the business tell this story. In Vol. XIII of the London Garden I find an English translation of M. Lachaume's book, "The Cave Mushroom," and this comment by the editor: "The most complete account of the cave culture of mushrooms which has been published by any cultivator on the spot well acquainted with the subject is that recently published by M. Lachaume."
Lachaume says: "The best spawn to use is what is called 'virgin spawn'; that is to say, which has not yet produced mushrooms. In this country this kind of spawn may be procured of any respectable nurseryman, under the name of 'French spawn.' It differs from English spawn by being in the form of small tufty cakes, instead of in compact blocks. Large mushroom growers, however, always provide themselves with their own spawn by taking it from a bed which is just about to produce its crop, or which has already produced a few small mushrooms.... It is true that by thus 'breeding in and in,' as it were, the mushrooms show a tendency to deteriorate after a time; new spawn must therefore be obtained as soon as any signs of deterioration begin to manifest themselves."
Making French Virgin Spawn.—Condensed from Lachaume's book on mushrooms. Take five or six barrow loads of horse droppings that have lain in a heap for some time, and lost their heat, and mix them with one-fourth of their bulk of short stable litter. Then, in April, open a trench two feet wide, twenty inches deep, and length to suit, at the foot of, but eight inches distant from, a wall facing north. In the bottom of the trench spread a layer three to four inches deep of chopped straw, then an equally thick layer of the prepared manure, all pressed firmly by treading it down. The two layers must now be gently watered, and then another double layer of chopped straw and droppings must be laid, trodden down and watered, and so on until the top of the trench is reached. The bed ought to rise above the level of the ground and be rounded off like the top of a trunk. To prevent excessive dampness from heavy rain cover the mound with a thick layer of stable litter. Three months after filling the trench it should be opened at the side or end. If the pieces of manure are well covered with masses of bluish-white filaments, giving off the odor of mushrooms, the operation has succeeded, and the spawn is fit for use or for drying to preserve for future use. But if the threads are only sparingly scattered through the mass, the trench should be covered up again and left for another month. In saving the spawn the flakes of manure containing the largest amount of spawn filaments should be retained, and those showing a brown appearance rejected. In order to facilitate the drying of the spawn the flakes should be broken into pieces, weighing from one to two pounds; they are then placed in a well ventilated shed, but they must not be piled upon each other. Properly prepared and dried this spawn keeps good for ten years.
A Second Method (by Lachaume). "This is generally adopted by mushroom growers. The formation of the spawn is accelerated by adding pieces of old spawn here and there.... At the beginning of April we must choose a piece of ground situated at the foot of a wall facing north.... The soil ought to be very open and light rather than heavy, so as to avoid dampness. Taking advantage of a fine day, we open a trench sixteen inches wide and at about eight inches from the foot of the wall, and of a length adapted to the quantity of spawn we desire to produce. The earth is thrown out on the side opposite the wall. Manure which has been prepared for a mushroom bed, and has just come into condition is then filled into the trench, leaving, however, a space at one end of it about two feet and six inches in length for the formation of a mushroom bed, which is made by tossing the manure about and shaking it up with the hands, after which it is pressed down with the hands and knees. As soon as the layer of manure reaches six inches in thickness we place along the edge a number of lumps of spawn at about one foot apart. These lumps are placed level with the manure on the edge facing the wall. This portion of the surface of the manure ought to be raised vertically, and should lean against the earthen wall of the trench. The other half of the surface ought to slope gently toward the wall, leaving a space of three or four inches between it and the side of the trench, so that it may be trimmed. The lumps of spawn on this surface should be placed a little backward, so that they may not be broken when the bed is trimmed. The bed is then covered with more manure, until the first lumps of spawn are buried three or four inches deep. A second row of lumps of spawn is then inserted, as described in the directions for making the first row, and the bed is filled up level with the surface of the soil. It is finished by covering it up with a layer of fine, dry soil three or four inches thick. The spawn ought to be very dry, otherwise we shall get a premature crop of mushrooms instead of fresh spawn. At the end of six weeks or a couple of months the new spawn ought to make its appearance, a fact which we may learn by opening the bed. One sign, which will save us the trouble of opening up the beds, is the appearance of young mushrooms on the surface. The layer of earth is first removed, and then the cakes of spawn are treated as described in the directions given for the first method of making spawn."