THALLOGENS. 253 
separates, and it becomes convex, or slightly conical, of a white or 
palish yellow, with rose-coloured gills, and a thick white fleshy 
cap. At a more advanced age the cap becomes concave, the colour 
grey, and the gills nearly black. A whitish membrane, like a 
species of veil, entirely covers the young gills, forming afterwards 
a sort of collar, more or less perfect, round the stalk. 
The field mushroom grows naturally upon the grass sward, 
where it is exposed to the sun. It is also obtained by culture 
in dark places where there is heat and moisture, as in caves and 
quarries. But it is necessary to guard against its being confounded 
with other species which are dangerous poisons; such are the Fly 
mushroom, A. muscarius and A. virosus, and a species of Amanita, 
which somewhat resembles it, although it is distinguished by 
the footstalk being bulbous at the base, enveloped as by a purse 
(volva), and by the colour of its gills, which are not rose-coloured, 
as in A. campestris, but of a pale whitish colour. That we may 
have some exact idea of the structure of the mushrooms in general, 
let us consider the structure of the comestible species. 
Let us detach one of the lamin or gills which occupy the lower 
face of the cap. We shall readily observe, by looking at it 
through a lens, that the two surfaces are of a velvety texture ; 
but it is only through the microscope that their true organisation 
can be appreciated. 
Ifa transverse incision is made in the thinner parts of these 
lamin, which shall be perpendicular to their surface, we may 
assure ourselves ocularly that each plate presents three very 
distinct beds. A middle bed in connection with the substance 
of the cap—a sort of layer, upon which the perpendicular elements 
of the two other beds rest. These elements consist of cells of 
three distinct kinds. (Fig. 319, 4). The first are shorter than 
the others, carrying nothing at their free extremity: the next 
are a little longer, terminating in four points, which each bear 
4 small spherical sac at their summit (Fig. 319, 5). The third are 
much larger, but have neither point nor sac at their extremity. 
We are assured by experiment that the little sacs, disposed in 
fours at the summit of the centre cells, are the reproductive organs 
which germinate and reproduce the mother plant. We call them 
“Pores ; the cellules which support them are called dasides. The 
