THE DEVELOPMENT OF SOME EXOGENOUS SPECIES OF 
AGARICS 
Gertrude E. Douglas 
In 1914, while looking for agaric material suitable for develop- 
mental studies, abundant young stages of several exogenous forms- were 
found. At that time Professor Atkinson pointed out the need of a 
thoroughly modern investigation of these forms, both on account of the 
incompleteness of the early work and because the method of gill 
development in the endogenous forms was at that time receiving con- 
siderable attention. It seemed important to determine if the method 
of gill formation of species, differing in the presence or absence of a 
universal veil but otherwise rather closely related, would show any 
very radical differences in the method of the formation of their gill 
salients. 
Until the work of Blizzard (9) in 19 16, no study of development 
of exogenous forms of agarics had been made with our modern methods 
of technique. A considerable number of exogenous as well as endog- 
enous forms^ were early studied by Hoffmann (17, 18, 19) and among 
them one species of Entoloma {E. sericeum Bull.). Although his work 
was of necessity somew^hat limited, he came to the correct conclusion 
with regard to the differentiation of the hymenophore primordium in 
the groove formed between the stem and pileus fundaments, which 
had been formed by the epinastic growth of the pileus hyphae. He 
also noted the formation of an even palisade layer before the appear- 
ance of the gill ridges. 
Four exogenous forms, among them being one Mycena {M. vulgaris), 
were studied by DeBary, whose final conclusion (13, 14) with regard 
to the formation of an even palisade layer, preceding the development 
of the gill ridges, agreed with that of Hoffmann (17, 18, 19). In addi- 
tion he emphasized the order of their development in a centrifugal 
manner from the stem to the margin of the pileus. 
In 1889 a great number of forms were studied by Fayod, but owing 
1 For a complete list of the early forms studied see Atkinson, G. P., Origin and 
development of the lamellae in Coprinus. Bot. Gaz. 61; 89. Footnote i, 1916. 
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