SPH ZROTHECA. II! 
in the penultimate cell of the row, while all other cells of the ascogo- 
nium are uninuclear (Fig. 40, G). This penultimate cell becomes 
the ascus; it is not to be regarded as the exact equivalent of any other 
cell of the ascogonium, and its two nuclei are not necessarily sister 
nuclei, for before the last cross-wall is formed in the ascogonium the 
distal cell may contain three nuclei, and of these any pair may remain 
in the penultimate cell. With further development these two nuclei 
fuse (Fig. 40, G, H). This fusion is comparable to the nuclear 
fusion occurring generally in young asci, and consequently it has not 
the significance of fecundation, but represents merely a vegetative 
union. In this connection it may be mentioned that the objections which 
Dangeard (’97) has raised against the true sexual process described 
by Harper do not seem to me to merit any serious consideration. 
Spherotheca represents one of the simplest and perhaps the most 
primitive forms of the true Ascomycetes, especially as regards the 
development of the ascogonium. In Hryszpfhe and Ascobolus a 
greater complexity in the development of the ascogonium obtains, but 
there can be no doubt as to the nature of their sexual organs and the 
fusion of their true sexual nuclei, especially in Arys¢phe.’ 
PYRONEMA. 
In Pyronema we have a form which possesses for us a twofold 
interest. I refer to the trichogyne-like organ borne by the odgonium 
and the multiple fecundation, or the fusion in pairs of two or more 
male with two or more female nuclei in the oogonium. 
The development of the sexual organs is briefly as follows: The 
cells of the mycelium from which these organs are developed are 
multinucleate. Both odgonia and antheridia arise from the apical. 
cells of thick hyphal branches, standing vertical to the substratum. 
The young oogonium is more spherical and can be distinguished 
from the young club-shaped antheridium standing by its side. Soon 
a small papilla appears at the apex of the oogonium, which event- 
ually becomes the conjugating-tube or trichogyne (Fig. 41, A. B). 
Both organs are multinucleate from the start, the number of nuclei 
increasing by division as the cells grow in size. ‘* The nuclear multi- 
plication, however, is out of proportion to the vegetative growth, 
so that when the sexual cells are mature they contain relatively to 
their size more nuclei than do the ordinary vegetative mycelial cells” 
(Harper, 1900, p. 341). A broad stalk-cell is cut off from the 
base of the odgonium at a relatively late stage in its development, 
1 For a detailed discussion of these processes and the phylogenetic significance of the ascus fruit, 
the reader is referred to the original papers of Professor Harper (’95, ’96, 1900). 
