138 BOTANICAL GAZETTE [AUGUST 
duration. The gametophyte body retains this massive form 
until after the resting period. 
The second period of growth begins by the formation of a cuneate 
apical cell. A terminal cell is cleft by a wall inclined about 30° 
with reference to the longitudinal axis of the spore; a second 
inclined wall bisects the first at an angle of approximately 90°; 
lateral walls complete the cuneate apical cell (fig. 41). The latter 
cuts off dorsal and ventral segments (fig. 42) as well as lateral 
segments (fig: 43). Such a method of growth is characteristic of 
the young gametophyte until about the time of antheridium 
formation. 
The growth of the third period is by means of a lenticular 
cylindric apical cell (fig. 47). The transition is somewhat irregular. 
Sometimes the apical cell is more or less equally divided; then the 
two halves simultaneously cut off cells (fig. 45) which correspond 
to the dorsal and ventral segments of the preceding form. The thal- 
lus in cross-section has the appearance of being medianally divided 
by a wall. Another transition form is shown in fig. 44. As the 
thallus becomes thicker the posterior angle becomes greater, the 
two faces being finally replaced by one which is curved. The cells 
cut off from the posterior face divide rapidly; as many as 6 segments 
may be formed before the next division occurs. The rapid division 
of the laterally placed cells causes the wings to be protruded out- 
ward and forward (figs. 46, 48, 49). There has been much dis- 
cussion regarding the method of branching. HormetsTER’ believed 
that the central papilla (“‘Mittellappen”) shown in fig. 14 was the 
seat of the chief apex; hence that there is no true dichotomy. 
LeITGEB‘ states that the origin of the central papilla is from a 
marginal cell. When branching takes place, the apical cell, 
instead of cutting off a lateral segment, divides equally or almost 
so; each of these daughter cells assumes apical characters.. The 
central papilla is produced by the crowding together of lateral 
segments from the two apical cells. It later develops into a 
central lobe corresponding to fused wings. Branching is essentially 
3 HorMEIsTER, W., Higher Cryptogamia. Ray Society. 1862. 
4Lerrces, H., Untersuchungen tiber die Lebermoose. 1882. Vols. II and III. 
Jungermannieen 
