172 BOTANICAL GAZETTE [MARCH 
structure was not clearly seen without good thin microtome 
sections, the same thing may exist in other perithecia and have 
been overlooked because the microtome was not used. The find- 
ing of such a structure in Gnomonia ulmea would tend to support 
such a hypothesis. ReppicK (29), working with Gwuignardia 
bidwellii, found that when the first asci were developing not nearly 
all the pseudoparenchyma was gone, and that, when crowded 
together by the growth and expansion of two asci, it gave the 
impression that paraphyses were present. He also expressed the 
opinion that these cells were absorbed by the growing asci. This’ 
case differs from that found in Gnomonia ulmea and also from that 
described by STEVENS in Desmotascus only in that the pseudo-. 
parenchymatous cells in the latter two fungi never appear to be 
crowded by the invasion of the asci. 
The asci originate from the basal portion of the perithecial 
cavity, and also from the sides to a point about halfway to the 
top. The perithecial walls are composed of from 10 to 12 rows of 
cells (fig. 1), the outer one or two layers of which have assumed a 
bright golden brown color. It is at about the time when the ostiole 
is being developed that this coloration of the wall begins. Until 
that time the wall has been entirely hyaline. From this time on, 
as the perithecia age, this color becomes constantly darker, until 
about midwinter, when it is almost black. The outer surface of 
the perithecium is smooth, and there are no loose hyphae connect- 
ing it with the leaf tissue in which it is borne. 
When mature the perithecia are nearly spherical or usually 
somewhat wider than deep. They vary considerably in size, but 
average about 250-300 in diameter and 150-200 y in depth. 
The ostiole is usually about 100 w long and 75 u wide, but may 
reach a considerably greater length. The size of the perithecium 
is so great that the upper epidermis is elevated in the form of small 
tubercles, and the beaks push out the lower epidermis in the same 
manner, before they break through it. They do not extend any 
distance beyond the outer surface of the lower epidermis, as do so 
many of the species of Gnomonia, but merely reach through it. 
When the over-wintered leaves have been soaked in water, the 
perithecia may be picked out with the point of a sharp scalpel, and 
