1910] BROW N—ASCOCARP OF LEOTIA 451 
mate cell are not sisters, but are composed of one nucleus from 
each of two pairs of sisters, it will be seen that every time either 
the ultimate or penultimate cell, if formed in the manner described 
above, gives rise to a hook, the distance of the relationship of the 
nuclei which fuse to form the nucleus of the ascus is increased. 
_ This can hardly be of any significance, however, in the case of 
_ L. chlorocephala, for, as will be shown later, two nuclei which are 
seems probable, therefore, that in Leotia the only use of the con- 
_ tinued growth of the ultimate and penultimate cells is to increase 
_ greatly the number of asci which can be formed from a single 
_ hypha. 
In L. chlorocephala the asci are also formed by another method, 
which probably occurs about as frequently as the one already 
described. In this case the tip of the hypha does not bend as much 
as in the first (fig. 39). When the nuclei have divided, a wall 
comes in between the two pairs of sister nuclei (fig. 40). That 
the two nuclei in each cell are sisters would seem to be shown by 
the fact that the hyphae appear to be too narrow to allow a side- 
by-side division of the nuclei, or for the nuclei to migrate past each 
other. There is, moreover, no evidence that such a parallel 
division or migration of the nuclei does occur. The two nuclei 
of the ultimate cell may fuse to form the nucleus of an ascus (fig. 
41), or they may give rise to the four nuclei of another hook (fig. 
42). That the asci and hooks in these cases are formed from a 
binucleate terminal cell is shown by the presence of the tip of the 
mate has grown out; figs. 37, 38, binucleate penultimate cell has formed ascus, while 
ultimate with nucleus from antepenultimate has given rise to hook; fig. 39, tip of 
ascogenous hypha with two nuclei; fig. 40, the two nuclei have divided to four and a 
wall has separated the two pairs of sister nuclei; fig. 41, two nuclei _ ultimate cell 
have fused to form sities of ascus; penultimate cell is growing out to give rise to 
hook or ascus 
43, penultimate cell (a) has not developed further, while ultimate has 
hook similar to sone vomeajesty in fig. 243 binucleate penultimate = bad ened — - 
formed ascus, while 
fig. 44, diagram illustrating multiplication of asci by ‘method shown in figs. 39-. 43; 
fig. 45, diagram of structure of ascocarp of Leotia; fig. 46, diagram of structure of 
ascocarp of Pyronema omphaloides; fig. 47, diagrammatic comparison of conjugate 
divisions in Leotia and in the rusts; figs. sos X 2100. 
