70 
POPULAR SCIENCE REVIEW. 
Fries, of Upsala, following the views not long since published 
by the writer of these lines, now places the species in a new 
subgenus of Agaricus, — Claudopus ( Hymenomycetes Europcei , 
Epicriseos , p. 213), and says, under Agaricus ( Claudopus ) 
variabilis : “ Ad ligna et truncos emortuos, prsecipue 
Abietis.” 
In illustration of the hymenium, or reproductive surface of 
the gills in the Hymenomycetes , Professor Sachs gives a figure 
of the minute structure of the common mushroom ( Agaricus 
campestris ). But,, unfortunately, the figure and description 
alike are far frdm correct. Sachs says the basidia in this 
species produce only* two spores, whilst in other Hymenomy- 
cetes the number is usually four, and the illustration is made 
to accord with the description. But the fact of the case is that 
there are four spores produced in each basidium in Agaricus 
campestris , and this fact does not apply to A. campestris alone, 
but to every variety of it, and every variety of its numerous 
allies, of which the common horse mushroom (A. awensis ) is 
one. The nature of the hymenium of the common mushroom 
is correctly figured by Dr. M. C. Cooke, in the “Popular 
Science Keview” for Oct. 1869, PI. LIII. fig. 14, where each 
basidium is shown, furnished with four (not two) spicules. 
Each of these spicules normally bears a spore, but it is a com- 
mon thing in Agarics for the four spores to be produced two at 
a time, diagonally ; as the first two spores become ripe, two 
other and younger spores appear on the spicules at right angles 
with the first, and the two latter push the two former off. 
Sachs was evidently unacquainted with this fact. Seeing only 
two spores at a time on the basidia of the mushroom, he over- 
looked the fact that two had already been pushed off, or were 
not yet produced. It is, however, quite common to see all four 
spores produced at the same time in the mushroom, so that 
there is not the slightest foundation for reducing the basidia in 
Agaricus campestris to the production of two spores only. 
Le Maout and Decaisne, in their “ Descriptive and Analytical 
Botany,” p. 953, correctly figure the basidia in A . campestris 
with four spores ; but, unfortunately, the description of refer- 
ence to the basidia and the analogous organs (cystidia) is far 
from correct. These authors are still more incorrect under 
their description of Geaster hygrometricus (p. 956), one of the 
starry puff-balls, and, like the mushroom itself, one of the 
Basidiomycetes, This species is described by Le Maont and 
Decaisne as a hypogeal globose plant, which, they say, presents 
the following curious phenomenon : “ when mature and still 
underground, if the season be dry, the outer envelope, which is 
hard, tough and hygrometric, divides into strips from the crown 
to the base ; these strips spread horizontally, raising the plant 
