AGARICUS ARVENSIS AND A. COMTULUS 
5 
and white. There was a faint odor and taste of almonds. M. 
Boudier, to whom specimens were sent, confirmed the identification as 
Ag. arvensis. It is therefore a peronate variety of Agaricus arvensis 
comparable with Agaricus perrarus Schulzer,^ which is considered by 
some to be a form of Agaricus augustus Fr. Similar forms of Agaricus 
subrufescens Peck^ are sometimes found, which perhaps are identical 
with Ag. perrarus Schulz. while the normal forms of Ag. subrufescens 
Pk. are very near to Ag. augustus Fr., and this Ag. subrufescens, 
perhaps, may be considered a slender, small-spored variety of Ag. 
augustus. 
Another form intermediate between this strongly peronate form 
of Ag. arvensis, and the forest form (no. 21054), was found not far from 
the fairy ring described above. This (no. 24763) plant was growing in 
the edge of a small clump of bushes and small trees situated in the 
pasture, and was fully expanded. It was 20 cm. high, the pileus 
15 cm. broad and the base of the stem 4 cm. thick. The pileus was 
white, smooth or with delicate appressed scales. The annulus was 
large, membranous, and the under surface with large regular scales 
near the margin, radiately arranged. The stem was smooth, at first 
white, then later slightly rufescent and minutely scaly over the upper 
part of the fusoid bulb or base. There was a slight odor and taste of 
almonds. 
Agaricus arvensis is therefore quite variable in the Jura Mountains 
according to location and other conditions. A number of different 
varieties of Agaricus arvensis are recognized by some authors, though 
there will probably always be differences of opinion as to the limits of 
this and related species, because of their great variability, and because 
of different opinions as to the concept of species. But it seems quite 
reasonably certain that the material from which this study of develop- 
ment is made belongs to a forest form of Agaricus arvensis. 
DEVELOPMENT OF AGARICUS ARVENSIS 
Primordium of pileus, stem and hymenophore 
Early differentiation of the interior of the carpophore. — Fruit bodies 
2.5 mm. long by 2 mm. in diameter show a faint differentiation of the 
internal portion into pileus and stipe fundaments, but the peripheral 
2 Verhand. K. K. Zool. bot. Ges. — : 493. 1879. See also Bresadola, J. Fungi 
Trid. 1: 54- pl- 89. 1887. 
3 Described in 6th Rept. N. Y. State Mus. Nat. Hist. 25. 1893. 
