H4 MORPHOLOGY 
ing in function the suppressed seta. It is formed by the elongation 
of the axis of the leafy branch beneath the sporophyte, and as it bears 
the capsule at its summit, it resembles an ordinary elongated seta (fig. 
250). Of course the foot of the sporophyte 
is embedded in its tip. 
Conclusions. The Sphagnales present 
a remarkable mixture of liverwort and 
moss characters. The simple thallus 
body of the gametophyte resembles that 
of the anacrogynous Jungermanniales; 
the special leafy sex branches suggest the 
acrogynous Jungermanniales ; while the 
sporophyte is organized as in the Antho- 
cerotales. On the other hand, the erect 
leafy branches of the gametophyte and 
the operculum of the sporophyte are both 
distinctly moss characters. In addition to 
these characters in common with liver- 
worts and true mosses, Sphagnum possesses 
FIG. , S o.-Spkagnum: sporo- Qther characters pec uliar to itself, 
phyte, showing the globular cap- 
sule with operculum (lid) and' It was remarked that the simplest con- 
dome-shaped mass of sporogenous ceivable liverwort would be produced by 
tissue (in tetrad stage), the very combining the gametophyte of Pdlia with 
short neckhke seta, the bulbous * * 
foot embedded in the apex of the the sporophyte of Riccia. So in produc- 
leafy axis (gametophyte), which is ing Sphagnum, one might imagine a corn- 
extended beyond the leaves to bination of the gametophytes of the two 
form the stalklike (seta-like) 
pseudopodium. groups of Jungermanniales with the spo- 
rophyte of Anlhoceros. 
The features of Sphagnum that distinguish it from true mosses in 
general are (i) the thallose gametophyte, (2) the axillary antheridia, (3) 
the dome-shaped sporogenous tissue derived from the amphithecium, 
and (4) the pseudopodium. 
Such a form is often called a transition form, but better a synthetic 
form, for it combines the characters of several groups. 
(2) ANDREAEALES 
General character. This group comprises a single genus (Andreaea) of sili- 
ceous rock mosses. Sphagnum is hydrophytic, but Andreaea is very xerophytic. 
