MONOGRAPH OF THE LAUOULBENIACKJE. 



223 



17-20. In fig. 17, the primary wall-cells (fig. 15, »,») have undergone their first 

 division, having each separated into an upper and a lower cell and «'). The lour 

 cells of the inner series (»") have also been developed from the three basal cells (o,o); 

 but, although they extend upward above the septum which has divided the wall-cells, 

 they are not themselves as yet septate. In fig. 18, the wall-cells remain as before, 

 but each of the cells of the inner series has divided into two, (p c) the parietal cells 

 and (nc) the primary canal-cells. In fig. 20 the primary canal-cells have again 

 divided into two (n c' and nc"), and this division has been preceded by a correspond- 

 ing separation of the upper wall-cells (w, w) into the two cells (iv x and ivx). This 

 condition continues until the asei have reached a considerable development (fig. 23) ; 

 but before any of them are mature a last division takes place, by which the cell {nc") 

 of the same figure is separated into the cells (cc) and (tc) of fig. 24, and the cells 

 (iv x) are separated into {ivy) and (wz). In Stigmatoinyces, then, there are present in 

 the mature perithecium, before the spore discharge lias commenced, an outer series of 

 wall-cells disposed in four longitudinal rows of four cells each, the terminal cells of 

 which may be conveniently called the lip-cells, and also an inner series of cells 

 alternating with the outer, and also arranged in four longitudinal rows, each made 

 up of four cells, the lower of which may be conveniently termed the parietal cells, 

 the three others being distinguished as the canal-cells. There are thus four parietal 

 cells, twelve canal-cells and sixteen wall-cells, making a total of thirty-two cells in the 

 perithecium proper, exclusive of the three basal cells, the stalk-cell and the secondary 

 stalk-cell previously alluded to {o, h, andp of fig. 15). 



The asci, in the mean time, have continued to bud from the ascogenic cells, so that 

 their total bulk has greatly increased, and as a result the ascus mass begins to exert 

 a considerable pressure in all directions on the surrounding cells. In this way the 

 superior supporting cell, the secondary inferior supporting cell, and the parietal cells 

 are gradually destroyed, and in most instances, though not usually in that which has 

 been used as an illustration, the inferior supporting cell is eventually obliterated by 

 pressure. In Stigmatoinyces the lower series of neck-cells (fig. 24, n c) become 

 gradually inflated towards their distal ends and their walls are somewhat thickened, 

 so that they act as guard-cells which control, to some extent, the passage of the spores 

 from the general cavity of the perithecium to that of the neck. The asci as they 

 mature are sloughed off from the ascogenic cells, and rapidly disappear, their walls 

 being absorbed as soon as the spores are completely formed, so that the latter lie 

 free in the cavity of the perithecium. The spore mass thus formed, being constantly 

 augmented, pushes between the guard-cells (nc) just mentioned, and being forced still 



