415 



membrane or wall as an egg is enclosed in its shell. The spore is very 

 light and may float about in the air for a very long time, or may be 

 carried by the wind for many miles. When, however, it chances to 

 fall upon a suitable substratum, which is sufficiently moist and warm, 

 it germinates, that is, a little threadlike hypha grows out from one 

 side and into the substratum, and there it continues to grow and 

 branch and forms the mycelium or plant body. 



The mycelium sometimes grows cjuite rapidly, but sometimes rather 

 slowly, and it may take weeks or months or even years for it to mature 

 sufficiently to be ready to produce fruit. When it has matured and 

 the conditions for fruiting are suitable, if it happens to be a fungus 

 that produces umbrella-shaped mushrooms, little knots or knobs ap- 

 pear, here and there, on the threads of the mycelium. These are very 

 small at first but they gradually enlarge and finally become large 

 enough so that they begin to project above the surface of the soil or 

 other substratum. These structures are developing fruit-bodies or 

 mushrooms, and in this very young stage they are spoken of as "but- 

 tons" or button stages. If we were to cut one of these buttons in 

 two, lengthwise, we would find that it is already a little umbrella, but 

 the umbrella is closed and is entirely covered with a membrane or 

 veil which is called the outer or universal veil. Page 416 shows several 

 stages in the development of one of these buttons into a mushroom. 

 The species sht^wn there is Amanita vcnia, "the destroying angel", a 

 very pretty but deadly-poison plant. It will be seen from the photo- 

 graph that as the button grows the outer veil, after being stretched 

 to its limit, is broken. In this species it splits at the top and remains 

 at the base of the stem as a cup-like structure, sometimes called the 

 "death-cup", but more properly called the volva. The great majority 

 of mushrooms, however, do not have a volva, because the outer veil 

 is torn loose at the bottom and remains wholly or in part on the top 

 of the mushroom, or is so thin and delicate that it disappears entirely, 

 and no trace of it can be seen. 



There is a second veil, called the inner veil, which extends from 

 the outer edge of the top part of the mushroom to near the upper end 

 of the stem. When the umbrella opens up, this veil is stretched to its 

 limit and finally gives way. In the case of Amanita vcrna, and a 

 large number of other species, it is always torn loose at its outer edge 

 and remains on the stem, forming a ring around the stem. In some 

 species, however, it tears loose from the stem and clings to the outer 

 edge of the umbrella, and in a very large number of species it is so 

 delicate that it very quickly shrivels away and is rarely seen at all. 

 The fate of these two veils, as the mushroom develops, is very im- 

 portant, as we shall see later, in the classification of mushrooms. 



