A TEXT-BOOK OF BOTAXY. 



is attached to rocks by means of a slender hold-fast. The thallus 

 is dichotomously branching, somewhat flattened, but may be quite 

 linear. The fronds show a mucilaginous modification of the cell- 

 walls. In the upper segments occur small differentiated areas, 







FlG. 15. Specimen of C Imndrus cnspus still attached to the rock where it was found 



growing alony the Massachusetts coast. 



sometimes called sori, of a more or less elliptical outline, which 

 on sectioning are found to be in the nature of sporangia, contain- 

 ing numerous tetraspores ( Fig. [6). The spores are discharged 

 through narrow canals extruding through the more or less com- 

 pact outer layer of the frond. The article found in commerce has 

 the color removed by being bleached through the action of the sun 



