NOTES ON THE HISTOLOGY OF POLYSIPHONIA FASTIGIATA, 181 
pericentral and one intermediate cell, which latter subdivides into 
the mother o the tetraspores and the basal cell (‘ parallelo- 
gram” of Wrig 
Tam ee sf confirm this account of the mode of origin of the 
pevicentral and intermediate cells. The process seems to be one of 
inary, but incomplete, vison, The apical cell first of all seg- 
m cha transversely into a new apical cell and a disc-shaped segment 
connected by means of five very distinct strands of protoplas sm with 
the new apical cell. The disc then suffers division in four radial 
pane which, however, do not penetrate to the centre. One of the 
rms of the cross so formed (figs. 1-5) next segments radially into 
rag colle, which are destined to become pericentral cells. A ne 
cell is then cut off from the central cell to form the intermediate 
cell. The connection of the pe aoa cat with the perloaniee 
-thi 
also preparations which show the intermediate cell in 
connection with three pericentral cells; I have no doubt that the 
nection with even four pericentral cells 6) have observ 
isolated intermediate cells wi arene one obviously that 
by which it had been in co: ion wi cell, and four 
ec 
processes which had been in connection with rom pericentral cells. 
The intermediate cell, as soon as formed, por horizontally 
into a basal cel of the n which latter 
six division _ make their appearance, resulting in ‘the formation 
of four tetrahedra. One of these tetrahedra maintains for some 
time protoplasmic continuity with the rem cell, but when the 
tetraspores are ripe, the connection is interrupted by the formation 
of a “plug.” The tetraspores have special cell-walls inside the 
wall. 
growth in size of the tetraspores the sporiferous branch 
assumes an irregular tuberculate appearance, each swelling corre- 
frequently occurs. By the progressive enlargement of the spo- 
visti ib Spithebeckiel i ells are greatly distorted, as is also the 
central cell (fig. 7). The thick special cell-walls of the € pericentral 
cells separate, and the pressure being thus relieved, the sporangium 
is forced into the intercellular fl so formed. The cuticular 
wn 
rapture, sathctiats it always appears more granular at the spo 
where discharge of the tetraspores has taken place. 
(c). The pericentral intercellular spaces. oe Pa een the pericentral 
and the central cells, and at the level of the junction of the walls 
of two central cells, well-marked intercellular spaces occur, 
K 2 
