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Generitype [ Taxonomy ]
Synonym: Type species

Dictionary of botanic terminology - index of names

     
  A generitype (also called type species) is the type specimen of the nominal species typifying a genus or subgenus;  
     
The description of a genus is based primarily on its type species, modified and expanded by the features of other included species. The generic name is permanently associated with its type species. For example, the type species for the genus Opuntia is Cactus opuntia (currently recognized as Opuntia ficus-indica). This name must be known as part of the genus; Cactus. Presumably, a type species best exemplifies the essential characteristics of the genus to which it belongs; this species then defines the genus for the purpose of deciding whether other species belong to that genus or not.

See: Type, holotype,

 


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Holdfast roots  [ Botany  ]

Dictionary of botanic terminology - index of names

 
     
  Some species of climbing plants develop holdfast roots which help to support the vines on trees, walls, and rocks. By forcing their way into minute pores and crevices, they hold the plant firmly in place.  
     
Climbing plants, like the poison ivy (Toxicodendron radicans), Boston ivy (Parthenocissus tricuspidata), and trumpet creeper (Campsis radicans),  develop holdfast roots which help to support the vines on trees, walls, and rocks. By forcing their way into minute pores and crevices, they hold the plant firmly in place. Usually the Holdfast roots die at the end of the first season, but in some species they are perennial. In the tropics some of the large climbing plants have hold-fast roots by which they attach themselves, and long, cord-like roots that extend downward through the air and may lengthen and branch for several years until they strike the soil and become absorbent roots.

Major references and further lectures:
1) E. N. Transeau “General Botany” Discovery Publishing House, 1994
     

 

 

 

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