THOMPSON: THE MORPHOLOGY OF TAENIOMA 101 
which come the long narrow monosiphonous hairs (1—many 
cells in length) at the apex (Fics. 6, 7, 8). In the case of the 
plant having three hairs, the formation of the third hair presents 
no variation. After the second apical cell has been separated off, 
the larger lower cell again increases laterally and a third cell is 
formed by division. After the hairs begin their formation no 
further transverse split takes place in the branch cells already 
formed, thus fixing definitely at this point the number of segments 
in a mature branch. The first divisions of the branch cells are 
similar to those of the stem. Two longitudinal divisions split the 
filament into a plate of cells in three rows (FIG. 10). But now a 
characteristic change takes place in the two outer rows. In these 
cells an oblique wall, first occurring in the upper half, splits off a 
triangular cell one third the size of the original, then a second of 
like shape and size in the lower half, forming three cells: an inner 
pericentral cell of the same height but one half the width, and 
two outer marginal cells, one lying above the other, one half as 
long and one half as wide as the original cell (FIG. 9). Simultane- 
ously with these divisions two longitudinal ones in the central row 
of cells divide it into a midrib, three cells in thickness. These 
divisions all begin at the base of the branch and proceed to the 
apex. A flat-branch segment in distinction from an axis segment 
now.consists of nine cells; three in the midrib, a pericentral cell 
on each side of the midrib, and beyond each of these two small 
marginal cells. These segments are of a similar structure through- 
out the branch with the exception of 2-4 at the base, which do 
not form the small marginal cells, but have four pericentral siphons 
like those of the main axis. 
Up to the present time, so far as my knowledge goes, the 
tetraspores have been the only known organs of reproduction of 
Taenioma. These have been mentioned both by Bornet and 
Thuret, and by Agardh. Bornet and Thuret (’76) merely figure 
and describe very briefly the gross appearance and position of the 
stichidia with no account of the tetrasporic formation. Agardh 
(63) gives a fuller account, but yet does not satisfactorily present 
in detail all cell divisions taking place in the stichidia. This ac- 
count will supplement both the above, as well as the later descrip- 
tion and figures given by Falkenberg. In the material examined, 
