CHAPTER VIII. 

 THE ROOT. 



69. True roots. — It has been pointed out that, among the 

 lower plants, there are very many which possess structures 

 similar in form and function to the root, and by some called 

 by this name. Although these parts serve to hold the plant 

 in place, and perhaps to absorb material from the substratum, 

 they are not to be looked upon as equivalent to the roots of 

 the higher plants either in origin or structure. In the algae, 

 fungi, liverworts, and mosses, the gametophyte is the promi- 

 nent phase. In no case does the gametophyte produce true 

 roots. It is not until the sporophyte becomes an independent 

 plant that true roots are found in the vegetable kingdom. It 

 is, therefore, only among fernworts and seed-plants that these 

 organs are to be found. When the sporophyte is developed 

 as an independent plant, it becomes necessary for it to pro- 

 duce some organ capable of holding it in place, or of absorb- 

 ing materials from the outside, or of doing both. The organ 

 developed to meet this need is the root. 



70. Primary and secondary roots. — In accordance with 

 their origin, roots are either primary or secondary. Primary 

 roots are the first formed roots, i.e., those which are de- 

 veloped directly by the young embryo. In both fernworts 

 and seed-plants the primary root is rarely wanting, but often 

 short-lived, dying after the plant has established itself and 

 has formed secondary roots to take its place. In many cases, 



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