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the soral components and in the 

 average number of gonidia seem to be 

 constant for the different species. 



Inasmuch as the same problems of 

 maintenance confront kelps and large 

 land plants, one is not surprised to 

 find similar physiological tissues in both 

 kinds of organisms. Thus both have 

 the limiting layer, the epidermis; both 

 the photosynthetic areas, the chloro- 

 phyll-containing cells; both the strength- 

 ening areas and skeletal apparatus, with- 

 standing the shock of the waves in 

 one instance and the impact of the 

 wind in the other; both the conduc- 

 tion paths, the reserve tissues and the 

 sporogenous tracts. Indeed, the con- 

 ditions are not so very different after 

 all, for land plants may be regarded 

 as submerged in the atmospheric ocean, 

 subject to its currents, changes in den- 

 sity and temperature, just as plants 



