50 



PLANT LIFE. 



that of some of the green algae. The body is a thallus with 

 rhizoids (fig. 57). The rhizoids are usually linear aggregates 



Fig. 57. — A, plants of Riccia sorocarpa, on the ground. Gametophyte phase. Nat- 

 ural size. B, a vertical section of one of the thick lobes of the thallus, showing 

 nearly uniform structure. The thallus has nearly covered over two young sporo- 

 phytes which appear as though in the interior. Rhizoids arise from the ventral side 

 and flanks. Magnified about 25 diam. — After I5ischoff. 



of cells having thin walls and little protoplasm, arising from 

 the under side and flanks of the thallus. They serve to 



Fig 58.— Portion of a vertical section of the thallus of Lunularia cruciata. a, 

 dorsal, i, ventral epidermis; c, an air-pore; <•, air-chamber, from whose floor rise 

 cell-rilainrnis, ,/ ; _/, partition between adjoining air-chambers; g; colorless cells 

 containing starch, some showing net-like thickenings of the walls, others with oil- 

 bodies, //; 1, a ventral scale ; /, a rhizoid. Magnified 110 diam. — After Nestler. 



fasten the thallus to the substratum, — an adaptation to the 

 terrestrial mode of life. The thallus is usually fiat and 



