CHAPTER X 

 THE VASCULAR PLANTS 



75. Introductory. — Vascular plants are plants with a 

 vascular system. A vascular system is composed mainly 

 of large cells called vessels. This system is the principal 

 means of mechanical support and of sap movement for 

 such plants as possess it. The fern plants and the seed 

 plants possess vascular systems. Plants of the lower 

 groups do not. 



The greatest gap in the plant kingdom is between the 

 vascular and the non-vascular plants. From the simplest 

 thallophytes to the most complex bryophytes there is a 

 sort of series of forms which gradually increases in com- 

 plexity. Also from simplest pteridophytes to highest 

 spermatophytes a similar series may be traced. But be- 

 tween bryophytes and pteridophytes there is a great gap. 

 Here there are many " missing links " in the chain of plant 

 evolution. 



A vascular system is to a plant all that your blood vessels 

 and bones are to you. It forms the principal paths of move- 

 ment in the plant, as well as the mechanical support which 

 enables it to stand erect. You have learned of this in 

 your study of stems (Chapter V). The vascular system 

 is composed of xylem and phloem, two groups of tissue 

 that are always found together, usually in the form of what 

 are called vascular bundles. (See page 82.) 

 Vascular plant bodies are all sporophytes, the gameto- 



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