170 BOTANICAL GAZETTE [SEPTEMBER 
spermatogenous cell (jigs. 20, 22). When only a single primary 
prothallial cell is cut off, it may (fig. 19) or may not (fig. 21) divide 
again. Far more frequently it does divide anticlinally. No case 
in either species has been observed where either prothallial cell divides 
periclinally. In case two prothallial cells are cut off, both usually 
divide anticlinally (figs. 23, 26, 27), although the division may be long 
delayed or fail wholly (text fig. 4). The first one may remain undivided, 
or in rare cases may divide twice, so that the first tier of prothallial 
Ic. 1. Transverse section of a male gametophyte consisting of one pro 
F 
cell (p:), the primary spermatogenous cell (ps), and the tube nucleus ().—Fis. 
cells contains four cells. The second one almost always divides once 
and usually twice. Thus there may be one, three, four, six, OF eight 
prothallial cells; six is much the commonest number, and one or eight 
the rarest. In case only one prothallial cell is cut off, its nucleus 
