THALLUS OF PELLIA 



233 



growing on soil among damp herbage, or in marshes. 

 Pellia has no differentiation into distinct stem and 

 leaves, any more than Fucus has. The body con- 

 sists of a flat green thallus, which may be elongated 



FIG. 36. Pellia. A, plant (natural size) growing in bright light 

 with crowded branches; spn., sporogonia of various ages, the 

 oldest with long stalks and open capsules. B, part of thallus 

 on a larger scale, showing forking at the tip; rh., rhizoids arising 

 from lower side; a, antheridia; spn., sporogonium with opened 

 spore capsule showing bunch of hair-like elaters (el.). 



and band-shaped, or may (especially in bright light) 

 grow slowly in length and branch freely so that the 

 plant is tufted (Fig. 36). The margins of the thallus 

 (wings) are often " crisped " because they have grown 

 quicker than the thicker central part, or midrib. The 

 latter bears on its under surface brown rhizoids 

 (Fig. 36, B, rh.), which enter the soil and absorb from 

 it water and dissolved salts. 



A thin cross-section of the thallus shows that all 

 the cells are living and may contain chloroplasts, 

 though these are mainly concentrated in the upper 

 (sometimes also in the lower) surface layer. This 

 represents an incipient differentiation of photosynthetic 



