THE CULTIVATION OF MUSHROOMS 



1383 



add considerably to the price of these 

 articles, which, in quantity, may be pur- 

 chased much cheaper where made. It 

 is a useless expense to import a material 

 having such bulk as mushroom spawn. 

 There is nothing in the climate to ren- 

 der the manufacture difficult in America, 

 and good brick spawn is now being 

 made. 



When it is recognized that spawn 

 making may go hand in hand with mush- 

 room growing, some growers in this 

 country will doubtless wish to grow the 

 spawn needed in their own work. In 

 such cases the cheaper method of mak- 

 ing flake spawn may make it preferable. 



Virgin Spawn 



Whether the spawn is made as bricks 

 or as flake material, the point of great- 

 est importance is to secure a so-called 

 virgin spawn, or a new growth of the 

 mycelium of Agaricus cam.pestris, which 

 has never exhausted itself to any degree 

 by the production of mushrooms. The 

 problem of securing such virgin spawn 

 is a difficult one, and as usually met in 

 England and France it leaves to chance 

 the quality and other characters of the 

 mushrooms which may grow from such 

 spawn. If, accidentally, mushrooms are 

 found growing on the lawns or in pas- 

 tures, or if mycelium is located in such 

 situations, small trenches are dug be- 

 neath the sod and these are filled with 

 rich manure, with the hope that the vig- 

 orous-growing mycelium will penetrate 

 this manure in the course of a few 

 weeks. This usually occurs, and the 

 spawn is said to be very good when one 

 prevents the production of mushrooms 

 by this spawn, and, if possible, by any 

 of the mycelium in the vicinity. When 

 the manure in the trenches is well pene- 

 trated by the mycelium, the spawn is 

 removed and dried, and it is usually 

 termed virgin spawn. It may then be 

 used in the inoculation of spawn bricks, 

 or it may be used in the inoculation of 

 small beds, either of which, when pene- 

 trated by the growing mycelium, may in 

 turn be used as commercial spawn, brick 

 and flake, respectively, which is then 

 sold or used in a commercial way. 



In France, where the demands for vir- 

 gin spawn are very great, there may be 

 found persons who give their whole 

 time to a search for virgin spawn in the 

 various compost heaps which may be 

 found in the suburbs and throughout the 

 country. These persons readily recog- 

 nize the spawn of Agaricus campestris, 

 or, at least, one is led to believe that 

 they are very adept in such recognition, 

 and this virgin spawn, which is sup- 

 posed to have resulted from the germina- 

 tion of spores in the compost itself, is 

 sold to mushroom growers at a very 

 high figure. The growers use this spawn 

 in small beds, which, when well pene- 

 trated with the mycelium, will be broken 

 up and the contents of the bed dried 

 for general crop purposes. Whether the 

 virgin spawn is obtained in this way or 

 in the manner previously described, it 

 is a liaphazard method. The spawn from 

 a bed in full bearing, or that from an 

 old bed, should never be used in a com- 

 mercial way, for a light crop only may 

 then be expected. 



Pure-Culture Virgin Spawn 

 Artificial Production from Spores 



It will be evident from what has been 

 said that by such methods the exact 

 characteristics of the mushroom which 

 will be grown will not be known, unless 

 a special experiment is made to deter- 

 mine this before the crop is put in. Se- 

 lection or improvement of the common 

 varieties will, therefore, hardly be pos- 

 sible under such a system. Several 

 years ago it became evident to the writer 

 that for the development of the mush- 

 room work there was great need of 

 eliminating the "chance" method of se- 

 curing a good grade of virgin mush- 

 room spawn. It seemed that this might 

 be accomplished through a knowledge 

 of the conditions under which the spores 

 of Agaricus campestris germinated. The 

 Department of Agriculture has given 

 much attention to the investigation of 

 this problem during the past three or 

 four years. The results of the first ex- 

 periments along this line, conducted by 

 Miss Ferguson, were published in Bulle- 

 tin No. 16 of the Bureau of Plant In- 



