LABO ULBENIALES 



379 



and R. encijmonalis (Fig. 256, 5) appendages may develop from the distal 

 cells. Thus the receptacle is a flat ribbon lying upon the substrate, 

 usually attached by a unicellular, abruptly differentiated stalk with the 

 usual black foot. 



Fig. 255. — 1. Rickia pallida. Blackened cells, disorganized. 2. Rickia papuana. 

 Immature individual. 3. Rickia introversa. 4. Rickia dichotoma. Showing two parallel 

 axes. {After Thaxter, 1926.) 



Growth may be either apical or trichothallic as found in the basal 

 cells of the brown and red algae or a combination of both types. The 

 terminal cell of the germinating spore develops a primary appendage 

 with a two-celled base. The basal cell divides, cutting off the stalk cell 

 with the foot and leaving the upper cell from which all secondary growth 



