2082 



MUSHROOM 



MUSHROOM 



2406. Agaricus campestris (the true 

 mushroom). 



of Munich. "Toadstool" is a term which might well 

 be held sacred to the fairy tales of mushroom life. 



It seems probable that mushroom is derived from 

 the old French mouseron or moucheron, now mousseron. 

 An obsolete English form is musheron, while mush- 

 rump and mush- 

 rome have also been 

 used. Among con- 

 sumers of French 

 canned "champig- 

 nons" (fungi) there 

 seems to be the 

 feeling that this 

 general term is used 

 only for the culti- 

 vated forms, but 

 this is merely a 

 special trade use, 

 and even in popular 

 mushroom books 

 the cultivated 

 forms are carefully 

 distinguished as 

 " champignon de 

 couche." 



The only mushrooms cultivated extensively in Europe 

 or America are the "common mushrooms," or field 

 mushrooms, consisting probably of several closely 

 related species, which are usually designated Agaricus 

 campestris. In reality, there is a group of species, 

 including at least A. arvensis, A. campestris and its 

 near relatives, A. villaticus, probably A. Rodmani and 

 A. fabaceus, any of which may be cultivated. It is 

 not too much to hope that in time representatives 

 of several other genera of the fleshy fungi may be cul- 

 tivated for special purposes, but it is doubtful whether 

 any species in culture would yield more abundantly 

 than do the forms now grown. These species closely 

 resemble one another in general characteristics and in 

 life history, so that a description of a common type of 

 A. campestris will define all with sufficient accuracy for 

 the present purpose, and it will indicate in general the 

 terminology of all the Basidiomycetes, that is, the class 

 of fungi which contains the larger part of the fleshy 

 forms. 



Characteristics of Agaricus campestris (Fig. 2406). 



The full-grown expanded plant is somewhat 

 umbrella-like, with a central stalk (stipe) supporting a 

 rather thick cap (pileus). The stem may be from 

 2 to 5 inches in height, about 1 inch in diameter, and 

 above the middle there is typically a ring or annulus, 

 but there are no other appendages about the stem. The 

 cap bears on the under surface the gills, blade-like 

 lamellae reaching for the most part from near the 

 stem to the periphery of the cap. When the cap of the 

 young mushroom begins rapidly to expand, it breaks 

 away from its attachment to the stem, and the veil of 

 tissue which has hidden the gills from view is ruptured 

 at the periphery of the cap, leaving the ring or annulus 

 already mentioned. When the gills are first disclosed 

 they are of a beautiful pink color, but with age they 

 darken and ultimately become brown-black. 



The coloration of the gills referred to is due chiefly 

 to the formation of spores or propagative cells, in large 

 number. If one places the cap of a maturing mush- 

 room on a piece of white paper, gills downward, pro- 

 tecting the cap from rapid drying out, a perfect spore 

 print of the brown-black spores may be made. The 

 number of these produced by a single mushroom 

 expressed in figures is too great to be adequately 

 grasped. The spores are small ovoidal cells, as shown in 

 Fig. 2407, and they are borne upon club-shaped struc- 

 tures termed basidia, these being organs which are 

 characteristic of the whole class of the Basidiomycetes. 

 The entire surface of the parallel gills is studded with 



the basidia, each basidium bearing from two to four 

 spores. 



Vegetative and fruiting stages. 



In the open the spores doubtless germinate, but the 

 conditions for their germination are not so well under- 

 stood that they can be readily duplicated in the labora- 

 tory. At any rate, germination of the spores yields a 

 mycelium or thread-like growth that is characteristic of 

 most fungi. The development and growth of the 

 mycelium in rich earth, compost, or manure yields a 

 characteristic "spawn," for "spawn" is merely the 

 abundant development of the mycelium, or vegetative 

 stage of the fungus, in any suitable substratum. In 

 this connection it is well to note that the mycelium of 

 other fungi may invade a great variety of substrata. 

 Rich earth, the moist leaves of the forest floor, fallen 

 timber, and even the trunks of living trees are all 

 invaded by a variety of species, each having its par- 

 ticular growth-requirements. Fresh spawn of Agaricus 

 campestris has a fine aroma of mushrooms combined 

 with that of almonds. By this aroma alone it may be 

 easily recognized, and therefore distinguished from the 

 mycelium of common mould fungi. By pure-culture 

 methods, mushroom spawn may also be developed 

 from fragments of the tissue, as subsequently indicated. 

 Spawn is appropriately called the vegetative stage 

 of the fungus. 



The mycelium not only absorbs from the substratum 

 the necessary water, together with the organic and 

 inorganic food materials necessary for its immediate 

 growth, but obviously there is accumulated a con- 

 siderable amount above the growth needs, which serves 

 as a fine adjustment to the heavy demands for food 

 made somewhat later when fruiting begins. With a 

 vigorous development of spawn in earth or compost, 

 fruiting, or mushroom formation, will proceed. At this 

 time the threads of spawn become more strongly corded 

 and matted, attended by the formation of spherical 

 "pinheads," and the latter develop directly into the 

 well-known "button" stages, the appearance and rapid 

 development of which give such satisfaction to the 

 novice in mushroom-growing. With the increase in 

 size of the button and the differentiation of gills, there 

 is next a rapid expansion of the cap and the elongation 

 of the stem, followed by the rupture of the veil. The 

 mushroom is then full grown, at which time the shed- 

 ding of spores begins. 



Mushroom-culture. 



In times past, it has been the custom to regard mush- 

 room-growing as more or less of a mystery. It was 

 therefore con- 

 sidered impos- 

 sible to lay down 

 specific rules for 

 the guidance of 

 others. This was 

 due primarily 

 to the fact that 

 there had been 

 very little ex- 

 perimental work 

 from which to 

 deduce the prin- 

 ciples on which 

 successful cul- 

 ture depends. 

 There is now no 

 reason why an 

 intelligent per- 

 son should not 

 be able to pro- 

 duce mushrooms 

 successfully if he 



*P 



2407. Section of a gill of Agaricus cam- 

 pestris, enlarged: tr, trama; sh, hymen- 

 ium; b, basidium; st, sterigma; sp, spore. 



