114 
G. F. Atkinson, 
deBary 1 ) later reversed his position, and accepted the idea that, in A. 
campestris , as well as in other forms with a marginal veil, the primor- 
dium of the hymenophore was exogenous in origin, and later was covered 
by the over-growth of hypliae from the margin of the pileus and surface 
of the stem. 
But Fayod 2 ) (p. 284), in view of his results in the study of a large 
number of Agaricaceae with marginal veil, challenges the correctness of 
Hartig’s studies of Armillaria mellea , although this species was not in¬ 
cluded among the forms investigated by Fayod. 
An interesting situation in regard to the development of the fruit 
bodies in the angiocarpous agarics was thus created by Hartig’s account 
of the early stages of development in A. mellea. From the work of 
Fayod it became evident that in a large number of the angiocarpous 
forms, at least, the origin of the hymenophore is endogenous, although he 
studied neither A. mellea nor Agaricus campestris. From the conflicting 
statements of the earlier students, in the light of the work of Fayod, it 
was desirable that further studies of development should be undertaken, 
especially in the case of the two species last named. More particularly 
was this desirable because Hartig and de Bary, as well as the other 
early investigators did not have the advantage of our modern technique 
in sectioning and staining material, particularly that of the very young 
and delicate stages, but depended on free hand sections. When one 
attempts to make free hand sections of such minute carpophores, one rea¬ 
dily comprehends how difficult it is to make them thin enough for correct 
interpretation, and at the same time to retain the delicate mycelial elements 
in their normal position. Criticism, therefore, of these early investigations 
is not a reflection upon the ability or judgment of their authors. Such 
results are matters of history and the few errors are in themselves of 
little moment in contrast with the larger body of material in them which 
constitutes a real addition to knowledge. 
For more than two decades the situation in regard to these two 
species was one of confusion and doubt. Stimulated by the desirability 
of having this situation clarified, the writer, in 1905, having secured 
material of these two speecies in the necessary stages, undertook the study 
of development from the undifferentiated primordium of the carpophore 
through to the mature stage, by the paraffine and microtome method. 
The results of this study were presented before Section G of the „American 
1) de Bary, A., Vergleichende Morphologie und Biologie der Pilze, 
Myxomyceten und Bactérien, p. 312—315, 320, 18S4. English Edition, p. 290 
to 292, 297, 1887. 
2) Fayod, V., Prodrome d’une histoire naturelle des Agaricinés (Ann. 
Sc. Nat. Bot. VII, 9 , p. 181—411, pis. 6, 7, 1889). He says, “I am not in accord with 
de Bary and R. Hartig on the development of the angiocarpic forms.” “Although I 
have not been able up to the present time to see primordia of Agaricus melleus suffi¬ 
ciently young, I do not hesitate to declare that this point of view is incorrect. It can 
only rest on poor sections of stages already too old, for it is in absolute contradiction 
with the observations which I have made on well stained sections exactly in the 
median line of a considerably larger number of primordia of angiocarpous agarics. 
Besides, the figure of Hartig reproduced by de Bary in his „Pilze“ (fig. 133), 
approaches so little the appearance of my sections of stages of this agaric 3 mm long, 
that I willingly believe that this author has to a large extent made it diagrammatically. 
The lamellae of the angiocarpic forms are always developed on the interior of the 
universal veil (primordial cuticle), the continuity of which is only broken when the 
pileus grows more rapidly than it”. 
