1906] ATKINSON—AGARICUS CAMPESTRIS 255 
and stipe later, and it is interesting to note that W. G. SmirH?s in 
his study of Coprinus radiatus says that the cells of the pileus and the 
hairs which form the veil are the first to appear (/. c. 62), but his 
study does not seem to have been exact, and a comparison of such 
a form as Coprinus with Agaricus. (Psalliota) is not pertinent at 
present except as it bears on the attempt of some to formulate a 
general law of growth. oy 
If we.now turn to the law formulated by Scumrrz for the order 
of succession of the different parts of the pileate fungi, we see that 
A garicus campesiris does not conform to it, but that it is more in 
accordance with the idea expressed in the first sentence quoted from 
Friks, that all parts of the fungus unfold simultaneously. This 
must not, however, be taken wholly to support Fries’ conception 
of the young sporocarp nor his idea of central growth. While it is 
likely that a number of other fungi.will be found to agree with A gari- 
cus campestris in the mode of organization of the parts of the plant 
from the primordium of the sporocarp, it is certain that no law of 
Organization and succession of the parts can be formulated which 
will hold good of all the pileate fungi. There are probably some, 
as suggested above, in which the pileus and stipe primordia are 
organized before the primordium of the hymenium, and many others 
probably in which the stem is partially or quite well organized before 
there is even a primordium of the pileus, in which case the develop- 
ment would be in conformity with Scurrz’s law given above. This 
is very likely the case with certain long, slender-stemmed species of 
Marasmius, of such plants as Polyporus lucidus Leys. (Ganoderma 
lucida), and others. But we must wait until the different types have 
been carefully studied from the very young stages in microtome 
sections, 
Fayop (I. c.), who studied a large number of Agaricaceae, formu- 
lates the general law that the pileus is organized first within the young 
Primordium as a pileogenous layer (couche piléogéne), which arises 
by internal differentiation, marked by the more rapid growth of the 
hyphal elements and their richer content in protoplasm. This layer 
1S in the form of a shallow inverted bowl, convex above, concave 
below. This is surrounded on the sides and above by a thin layer 
5 Reproduction in Coprinus radiatus. Grevillea 4:53-65. pls. 54-61. 1875. 
