io8 
MORPHOLOGY 
Sporophyte. The sporophyte of Anthocerotales deserves special 
attention on account of its structure and on account of its degree of 
independence (figs. 239, 240). The outline of its development is as 
follows: the fertilized egg divides by a vertical 
wall (transverse in other bryophytes) ; subsequent 
transverse and vertical walls result in three tiers 
of four cells each; the three tiers produce foot, 
seta, and capsule. The innermost tier develops 
a foot which penetrates the thallus by rhizoid- 
like processes, and finally becomes a large bulbous 
structure (fig. 241). The middle tier, which also 
contributes somewhat to the foot, develops the 
so-called intermediate zone, corresponding in 
position to the seta of other groups. It is a 
region of active cell-division, continually adding 
to the capsule below, which thus becomes an 
elongated structure by basal growth (as distinct 
from apical growth). This growth may not con- 
tinue long, resulting in a short capsule (Noto- 
thylas, fig. 240); or it may continue long enough 
to result in a much elongated linear capsule 
FIGS. 239, 240. An- 
fA0cm*ite.-839,thaUusof (Anthoceros, fig. 239). Where the sporophyte 
Anthoceros bearing sporo- (sporogonium) emerges from the thallus, a 
phytes; the two sporo- tubular sheath is developed around its base by 
phytes to the nght show , 
the dehiscence by two &* tissue of the thallus. 
valves, leaving the colu- Capsule. The development of the outermost 
mella exposed; 240, thai- der b capsule f ormat ion is especially noteworthv. 
lus of Notothylas bearing 
sporophytes. By a series of transverse walls a number of tiers 
of cells is produced, and periclinal walls cut off a 
peripheral layer of cells (amphithecium) inclosing a group of central cells 
(endothecium). Among the Marchantiales and Jungermanniales there 
is the same setting apart of two regions, the amphithecium producing 
the capsule wall, and the endothecium developing the sporogenous 
tissue. Among the Anthocerotales, however, the two regions develop 
in a very different way. The endothecium does not develop sporogenous 
tissue, but forms a central axis of sterile tissue (columella), which in 
Anthoceros usually shows sixteen cells in cross section. By periclinal 
walls, the amphithecium becomes two-layered, and the inner layer is the 
sporogenous tissue, which thus caps the columella in a domelike layer; 
