260 BOTANICAL GAZETTE [OCTOBER 
Bohemia, and others), the basidia are two-spored. I have several 
times observed this fact in the cultivated mushroom. The illustra- 
tion of the hymenium of Agaricus campestris which I have used on 
two former occasions?® was made from a cultivated variety. GOE- 
BEL’s fig. go? shows only two spores on the basidium of Agaricus 
campestris, and this was probably also made from a cultivated variety. 
I have on the other hand several times observed that in case of the 
normal field or pasture form of Agaricus campestris there are four 
spores on a basidium. The nuclear phenomena in the formation 
of the spores have not yet been thoroughly worked out in the two 
spored forms of Agaricus campestris, but studies of C. E. LewIs 
carried on in my laboratory seem to show that the normal number 
of four nuclei are first formed in the basidium, and that two of them 
degenerate. This has been very. clearly shown by him to be the 
case in a new species of Amanita, A. bisporigera Atkinson.*° Nor 
has it been shown how the two-spored forms of A garicus campestris 
arise from the normal four-spored feral plant, or whether normal 
two-spored forms exist as constant types ia the field under natural 
conditions of environment, I have found a two-spored Agaricus 
resembling in some respects certain of the cultivated forms of 
Agaricus campestris growing spontaneously in the open, On one 
occasion it was found in June about young trees in a lawn which had 
been mulched with horse manure. On another occasion the same 
species was found on the hillside of a wooded ravine (Cascadill F 
gorge) on the campus of Cornell University. 
If there are two-spored forms of Agaricus campestris existing under 
natural conditions of environment which are constant and which 
present also other characters even slightly different, it would indi- 
cate that Agaricus campestris either is or recently has been passing 
through a mutating period, and that these forms are elementary 
species. Were the two-spored basidia the only differentiating char- 
acter, such a form might in the sense of DeVrres** be reg@ oa 
28 Studies and illustrations of mushrooms. I. Cornell Univ. Agr. Exp. Si® 
Bull. 168. fig. 189. 1897; and Studies of Am. fungi, etc. (/.) 
29 Outlines of classification and special morphology, Eng: ed., 1887. 
3° Lewis, C. E., The development of the spores in Amanita bisporigera 
Bor. Gaz. 41: 348-352. 1906. 
3¢ Species and varieties, their origin by mutation. 1905. 
Atkinson. 
