THE DEVELOPMENT OF STROPHARIA 
AMBIGUA 
Sanford M. Zeller 
(With Plates 124 and 125, Containing 12 Figures) 
In the fall of 1911, the writer's attention was called to an 
agaric which is very conspicuous in fir woods in the vicinity of 
Seattle, Washington, during the fall and winter months. Speci- 
mens have been collected as late as January 17. For this work the 
very young stages were collected in the fall of 1912. As far as 
the writer is aware, no study of the development of the genus 
Stropharia has been published and there appears to be doubt about 
the taxonomy of this particular species. 
The earlier literature on the development of the fruiting bodies 
of the Agaricaceae has been thoroughly reviewed by Atkinson 
(2), Allen (1), and Beer (3). In 1906, Atkinson found that in 
the early stages in the development of Agaricus campestris there 
was no differentiation, but a universal veil surrounded the homo- 
geneous mass of hyphae. The first differentiation was the pri- 
mordium of the hymenium in the form of a deeply stained ring a 
little above the center of the carpophore and lying some depth 
under the surface. The gill cavity forms below this hymenium, 
and the primordium of the pileus is distinguished from that of the 
stem and marginal veil. Next in the order of development the 
pileus becomes definitely outlined quite deeply under the surface 
by taking a deep stain. 
In the same year, Allen (1) found the development of Hypho- 
lorna to be different from that of Agaricus. In Hypholoma the 
universal veil is present from the beginning, and the first differen- 
tiation is a small central area which stains deeply. This differen- 
tiates successively into the primordium of the pileus, hymenium, 
and upper portion of the stem. The gill cavity is formed intern- 
ally after the formation of the primordium of the hymenium, and 
the lamellae are formed by the differential growth of the hyphae 
of the hymenial primordium. 
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