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A TEXTBOOK OF THEORETICAL BOTANY 



The second family is the Vitaceae, which are a family composed of 450 

 species arranged in eleven genera. The largest genus is Cissus, with 325 

 species widely distributed in the tropics and subtropics. The best known 

 however is Vitis, the vine (Fig. 1714), a genus once considered to contain 

 abouty forty species, but now split into several distinct genera. The plants 

 are tendril-climbing shrubs, which is the chief feature which separates 

 them from the Rhamnaceae. These tendrils (Fig. 1715) terminate the main 



Fig. 17 1 5. — Vitis vinifera. Axial tendrils. 



axis, which is continued by the growth of the uppermost lateral bud, so that 

 the tendril and leaf appear to be borne on opposite sides of the shoot, form- 

 ing a sympodium. The inflorescence occupies the same position as a 

 tendril. These tendrils may either terminate in a coiled, tactile tip or a 

 cushion-like adhesive disc. The fruit is a berry containing from one to 

 four seeds and is adapted for bird distribution. The plants occur all over 

 the northern hemisphere, though they may also be found at considerable 

 altitudes on tropical mountains. Species of Cissus however are sometimes 

 desert and steppe plants, in which the vegetative tissues become adapted 

 for water storage. 



Several are of economic importance, the chief of which is Vitis vinifera, 

 the Grape-vine (Fig. 17 16), which is wild in Asia Minor. Currants and 

 raisins are the dried fruits of varieties cultivated along the warm Mediter- 

 ranean coast. They have an abnormally high sugar content. The name 

 currant is a corruption of Corinth where the variety was first grown. In the 

 United States V. lahrusca (Fox-grape) is cultivated and several varieties 



