18 



BOTANY 



originally independent hyphae, and not the result of repeated cell- 

 division of a single primordium. 



Root and Shoot 



As the plant-body becomes more complex, the division of labor, 

 resulting in the development of special organs, is more and more 

 evident. The single cell, representing a root in the filamentous 

 Algae, may be replaced in the larger Seaweeds, which are often 



sp--- 



1 



ar 



FIG. 8. Fruiting body of a Fun- 

 gus (Ascobolus), showing a 

 spurious tissue composed of orig- 

 inally isolated elements. 



,-1 



plants of great size, by 

 powerful hold-fasts that an- 

 chor them firmly to the 

 rocks. These roots are sim- 

 ply organs of attachment, as 

 the absorption of dissolved 

 food materials is performed 

 by the whole surface of the 

 plant. In these large Sea- 

 weeds the upper portion, the " shoot," shows a more or less clear 

 division into the stem, or axis, and leaves, flat plates which comprise 

 most of the chlorophyll-bearing tissue. AVhile the leaves of the 

 common Gulfweed, for instance, are in structure and origin very 



FIG. 9. A, young plant of Nercocystis Ltit- 

 keana, one of the Kelps with the plant- 

 body differentiated into root, stem, and 

 leaves; much reduced. B, a Liverwort, 

 Blasia pusilla, the thallus showing rudi- 

 mentary leaves, I (X 3) . 



