Lemanectceae of the United States. 201 
In the sexual shoots of L. australis , L. nodosa , L . grand is i 
and some others, especially of the subgenus Lemanea , the cor- 
tical layer continues to grow until two or three layers of these 
cells are produced (see Figs. 41 and 46), each primary cell of 
the cortex producing serially a row of two or three short 
cells. 
As soon as the cells of the medullary layer are differentiated 
from the tie-cells, their radial faces being in contact, they in- 
crease in size very rapidly, thus exerting a mutual pressure 
which carries them together with the generative filaments 
away from the central axis. As the branching of the genera- 
tive filaments is more profuse in the region of the antherid- 
zone, the medullary cells are consequently more numerous, 
and the pressure here produces a farther movement of the 
wall from the central axis, and the c papillae ’ or enlargements 
appear. The central axis loses the concave faces which it 
first possessed and becomes cylindrical. 
In the progressive development of the layers the greater 
portion of the endochrome lies in a peripheral plane of the 
sexual shoot, so that at last the cortex is more highly colored 
than the interior cells. 
It will be remembered that, though each cell of the central 
axis corresponds originally in position to the axis of a primary 
cell of the young sexual shoot, in the mature sexual segment 
it articulates with the one above and below in the middle of 
the segment, and that the ray-cells are attached near the 
distal end of each cell. In the development of the primary 
cell, the axis elongates by growth chiefly toward the proximal 
end of the sexual shoot, so that its proximal end outgrows 
the descending generative filaments and reaches down into 
the segment directly below (Fig. 7 i). 
Very rarely there are variations from the normal arrange- 
ment of four descending and six ascending generative fila- 
ments in the subgenus Sacheria until near the antherid-zones, 
tie-cell results in a group of cells in the form of an inverted cone, the base of which 
is made up of the cortex. Each cell of the medullary and intermediate layers 
produces more than 2-3 outer cells. 
