318 



PELLIA. 



margin of the wings ; (2) the almost uniform structure of 

 the tissues, except that the lower cells of the midrib are 

 devoid of the chloroplasts which are present most 

 abundantly in the wings and the upper layers of {the 

 midrib; (3) the thickened bands on the walls of the 

 inner cells of the midrib seen better in longitudinal 



Fig. 67. PELLIA. Part of Longitudinal Section of Thallus, showing the 

 band-like thickenings on the walls of the inner cells. 



sections; (4) the rhizoids, each an unseptate outgrowth 

 of one of the cells of the lowest layer of the midrib. 



(6) In longitudinal sections through the midrib 

 some of the sections should traverse an archegonial cavity 

 ( 460) note (1) the tissues as seen in T. S. ; (2) the 

 vertical yellow or brown thickenings on the internal 

 cells, the bands running vertically in the tissue (Fig. 67). 

 In both transverse and longitudinal sections, note that the 

 cells of the internal tissue contain starch grains, and that 

 the rhizoids are unicellular though their free ends may be 

 branched slightly. 



