CHAPTER VII 



OTHER WAYS OF PROCURING FOOD AMONG THE 



HIGHER PLANTS 



All the world is little else in nature but parasites and sub-parasites. 



— B. Jonson. 



Classification of Plants. — The plant kingdom is divided into 

 four major divisions upon the basis of the structure and life history 

 of the plants concerned. These four divisions also differ in the 

 length of time that they have been upon the surface of the earth. 

 The simplest and least differentiated are the oldest, while the more 

 complex and most highly specialized are, in general, among the 

 newcomers on the earth. 



The oldest and simplest plants comprise the division of the 

 Thallophytes, which are plants without true roots, stems, or leaves. 

 They have developed along two diverging lines, one subdivision 

 comprising the Algae, which includes seaweeds, pond scums, and 

 other simple water plants. The Algae all contain chlorophyll and 

 are able as a result of this pigment to live independently of other 

 organisms. The Fungi, on the other hand, which are included in 

 the remaining subdivision of the Thallophytes, lack chlorophyll 

 and are consequently unable to manufacture their own organic 

 food. They will be discussed more fully in the next chapter. 



The second oldest division of the plant kingdom includes the 

 Bryophytes or mosses and their allies, the liverworts. They are 

 the simplest . land plants and, in practically all cases, are able to 

 manufacture their own food. 



The Pteridophytes form the third division of the plant kingdom 

 and include the ferns, scouring rushes, quillworts, and club mosses. 

 Here true roots, stems, and leaves are well established. The coal 

 deposits are largely made up of the carbonized remains of members 

 of this group. 



The most highly specialized and most recent plants form the 

 great division of the Spermatophytes, or seed-bearing plants. Most 

 of the plants of high economic importance are in this group, which 

 are now the dominant land forms and contain species well adapted 



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