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. ^.-Sphagnum: sporo- other characters peculiar 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 D 1 J 



foot embedded in the apex of the the sporophyte of Rtccta. So in produc- 

 leafy axis (gametophyte), which is ing Sphagnum, one might imagine a corn- 

 extended beyond the leaves to bination of the g ame tophytes of the two 

 form the stalkhke (seta-like) J 



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 (Andreaed) of sili* 

 ceous rock mosses. Sphagnum is hydrophytic, but Andreaea is very xerophytic. 



