120 
G. F. Atkinson, 
Summary. 
1. The very young carpophores, before any differentiation into their 
principal parts, show a differentiation into three zones, a central zone or 
area of fundamental tissue, an outer zone of septate radial hyphae and 
an intermediate zone of pseudoparenchyma, of small, irregular, mostly 
radially arranged cells forming a cortex. In the fundamental tissue are 
scattered slender, flexuous threads, rich in protoplasm and probably represen¬ 
ting elements active in growth. 
2. The first evidence of a differentiation into the fundamental parts 
of the fruit body is manifested in an endogenous, annular, limited area of 
more active hyphae not at first compacted into a tissue, forming the early 
» primordium of the hymenophore. The direction of growth and curvature 
of these hyphae, suggests the influence of epinasty. 
3. This epinastic influence extends to the tissue external to the 
annular primordium of the hymenophore, and thrusts the radial hyphae in 
this region, which were horizontal, downward at an oblique angle. Coin¬ 
cident with the further organization and development of hymenophore 
and pileus, the epinastic condition spreads upwards from this annular 
region causing the radial hyphae over the pileus to curve downward, more 
strongly toward the margin of the pileus, less so toward the center. The 
outer half or two thirds of these hyphae become more or less constricted 
at the septa giving to them a moniliform appearance. 
4. Beneath the hymenophore primordium, growth is less active, 
resulting in a loose meshed tissue which separates from the hymenophore 
and forms the internal annular gill furrow. In some cases active growth 
of this loose meshed tissue takes place, added to perhaps by growth of 
the tissue enveloping the stem, completely filling the gill cavity for a 
time. A palisade layer of active, rapidly growing hyphae next forms 
the well defined young hymenophore which soon becomes arched due 
to continued epinasty. These hyphae are at first very slender and sharp 
pointed but gradually change to, or are replaced by, a palisade of blunt 
hyphae. This is at first plain and even but later is thrown into radiating 
folds by the more rapid growth along the lines where the lamellae arise. 
5. The fundamental tissue beneath the young hymenophore becomes 
looser in texture forming with the zone of radial hyphae. the “marginal 
veil”. This increases in extent by growth and eventually is separated 
from the margin of the pileus and forms the annulus. The inner zone 
of this, of more delicate hyphae between the “universal veil” and the 
stem and continuous with the margin of the pileus, is the “partial veil”. 
6. The zone of radial hyphae, and a part at least of the cortical zone 
of the young carpophore of Armillaria mellea , probably is homologous 
with the radial and cortical zone in Lepiota clypeolaria, and thus homo¬ 
logous with the “universal veil” in certain species of Amanita and Ama- 
nitopsis, but does not become differentiated from the pileus as it does in 
these two genera. 
Explanation of Plates. 
The photomicrographs for figs. 1—6 and 8 were made with a Zeiss micro¬ 
scope, the object being 370. mm. from the sensitive plate. The combinations employed 
for the different figures were as follows: figs. 1, 2, oc. 8, ob. 1(3 mm.*, fig. 4, oc. 12, 
