The development of Armillaria mellea 
115 
Association for the Advancement of Science“, at the New Orleans Meeting 1 ), 
in the winter of 1905 — 6. The paper on Agaricus campestris was pub¬ 
lished in September 1906 2 3 ), while the only published notice of that on 
Armillaria mellea was by title. The photomicrographs obtained at that 
time, of the stages of development in this species, were not so satis¬ 
factory as could be desired. This led to a postponement of the publi¬ 
cation in the hope that new material might provide better sections, or 
that another trial of the old sections might result in better photomicro¬ 
graphs. After a delay of seven years the old sections have been reexa¬ 
mined with the result that they appeared to be more promising than was 
at first supposed. Accordingly in July 1913 I photomicrographed a 
number of the sections thus providing for the illustrations accompanying 
this paper. 
In the meantime Beer has briefly described the development of 
Armillaria mellea*). His work does not support Hartig’s account, for 
he finds that the primordium of the hymenophore is endogenous in 
origin, from the first covered by the veil. However, the case of A. mellea , 
is a rather critical one, since Hartig, in speaking of de Bary’s fig. 25 4 ) 
of Agaricus campestris , showing the annular cavity covered by the mar¬ 
ginal veil, said, in comparing it with his fig. 20, “it appears 5 ) from 
the agreement of the two figures that the conjecture is justified that, 
also by this last fruit body in the region of the hymenial tract, a 
subsequent growing together of the hyphae of the pileus and stem 
has taken place". Now, since Beer neither describes nor figures stages 
of the primordial carpophore prior to and at the moment of the first 
appearance of a structure indicating the differentiation of the primordium 
of the hymenophore, it might be contended that, the earliest stage presen¬ 
ted, his fig. 13, could be interpreted as in support of Hartig’s account. 
Beer’s fig. 13 really represents quite an advanced stage of the young 
hymenophore, and the very delicate veil with the hyphae from the margin 
of the pileus cortex curved downward leaves the situation still within a 
reasonable measure of doubt. Really, the principal justification for inter¬ 
preting this figure to indicate an endogenous origin of the hymenophore 
primordium, lies in the proof presented for an endogenous origin of the 
hymenophore by the studies on Agaricus campestris 6 ), Armillaria mucida 7 ), 
Hypholoma 8 ), and by the work of Fayod on other forms with a marginal 
1) Atkinson, G. F., The development of Armillaria mellea\ The deve¬ 
lopment of Agaricus campestris (Proc. A. A. A. Sc. 53 rd Meeting, Dec. 1905 to 
Jan. 1906. Ibid. Science N. S. 23, p. 203, 1906). 
2) Atkinson, G. F., The development of Agaricus campestris (Bot. Gaz. 
42, p. 215-221, pis. 7—12, 1906). 
3) Beer, R., Notes on the development of the carpophore of some 
Agaricaceae (Ann. Bot. 25, p. 683—689, pi. 52, 1911). 
4) de Bary, A., Morphologie und Physiologie der Pilze, Flechten 
und Myxomyceten , p. 68, 1866. 
5) Hartig, lt., Wichtige Krankheiten der Waldbäume usw., p. 25, 1874. 
6) Atkinson, G. F., The development of Agaricus campestris (Bot. Gaz. 
42, p. 241—264, pis. 7—12, 1906). 
7) Fischer, C. C. E., On the development of the fructification of Ar¬ 
millaria mucida Schrad. (Ann. Bot.- 23, p. 503—507, pi. 35, 1909). 
8) Allen, Caroline L., The development of some species of Hypho¬ 
loma (Ann. Myc. 4, p. 387—394, pis. 5—7, 1906). — Beer, R., Notes on the 
development of the carpophore of some Agaricaceae (Ann. Bot. 25, p. 683 to 
689, pi. 52, 1911). 
8* 
