87 
Nectria pallizena , Bres. 
observed developing in the internal tissues of the sterile perithecium, more 
generally near the upper part of the periphery. The rest of the sterile 
perithecium serves to increase the bulk of the sporodochium ; thus sections 
of sporodochia in pure culture often show layers of perithecia with walls 
of varying thickness. The fertile perithecium originates in the same way, 
and consists of the thick-walled outer layers and the thin-walled internal 
tissues with uninucleate cells. The nuclei of these cells are distinct and 
homogeneous and stain readily with the usual nuclear stains. Some of 
these cells eventually become absorbed, while others appear to divide and 
form several layers of delicate tissue immediately beneath the perithecial 
wall. On potato-glycerine the growth of the sporodochium is much looser,, 
hence the knots of hyphae which give rise to perithecia can be more easily 
distinguished. The appearance of the fungus, however, in no way tends 
to show that the conditions are not conducive to normal development. In 
the earliest stages, one or more cells in these knots are larger and sometimes 
binucleate (Fig. 23), but in such rapidly growing tissue this binucleate 
condition is probably due to division of the primary nucleus prior to cell 
division. The development of the firsfe stages of the perithecium is rapid, 
and difficult to follow. Before any disintegration of the central cells of the 
perithecium occurs, the ascogonia begin to develop (Figs. 15, 16, 19-22), 
and are easily distinguishable from the surrounding tissues, owing to their 
larger cells and denser cell contents. They are coiled multicellular structures 
with multinucleate cells, and the nuclei show a definite nucleolus and nuclear 
area. There is more than one ascogonium in the perithecium. In two 
instances three ascogonia could be counted with a fair degree of certainty, 
but the perithecia are so small at this stage, and the ascogonia so much 
intertwined, that it is difficult to trace each ascogonium throughout its 
length through a series of sections, and to determine whether the number 
of ascogonia varies in different perithecia. 
The ascogonia originate from thin-walled tissue at the base of the 
perithecium, and appear to push their way up amongst the central cells 
(Fig. 15). Some of the latter begin to disintegrate. Fig. 15 shows the 
bases of two young ascogonia in a young perithecium, and disintegrating 
central cells. It was not possible to determine whether the ascogonium 
begins as one cell and becomes multicellular by growth and cell division, 
or whethc^ it is a multicellular structure from the first, being gradually 
differentiated from a row of central cells. No case of an incipient uni- 
cellular ascogonium was observed, but the examination of a considerable 
number of young perithecia in different stages led to the conclusion that 
the multicellular condition was most probably due to growth and cell 
division of a differentiated primary cell. The cells of the ascogonia 
increase in number as the perithecium develops, until a stage is reached 
in which the interior of the perithecium is filled with a considerable number 
