THE DICOTYLEDONES 1743 



Not all the Urticaceae possess stinging hairs though they are present 

 in the genera Urtica, Urera and Laportea. In the two latter genera the 

 effect of the sting is serious and may cause severe injury to those who 

 come into contact with the plants. 



Fig. 1620. — Urtica dioica. Common Nettle. 

 Male plant in flower. 



Certain genera are used as a source of fibres, among the more important 

 being Boehmeria. It is chiefly cultivated in China, where the fibres of 

 B. nivea (China grass or Rhea) are obtained from the inner bark. They are 

 possibly the toughest, longest and most silky of all vegetable fibres, reaching 

 a length of up to 9 in. In the tropics a variety tenacissima is cultivated under 

 the name of Ramie. Though these fibres are very valuable they are the 

 most difficult to prepare. Smaller fibres up to 3 in. long can be obtained 

 from the Stinging Nettles. 



Anatomically the Urticaceae are of note because of the cystoliths which 

 are found very commonly in the epidermal cells. They vary in shape in the 

 different genera. A milky latex common in the Moraceae is absent from the 

 Urticaceae. 



The Moraceae are a family of some 900 species which are very widely 

 distributed in the warmer parts of the world. There are some fifty-five 

 genera, of which the genus Ficiis is easily the largest. They are mostly 

 trees or shrubs with stipulate leaves and many are of economic importance. 

 The inflorescence (Fig. 1 621) is cymose or racemose but is frequently modi- 

 fied. The flowers are unisexual. The perianth consists of four segments 

 which are occasionally united. In the male flowers (Fig. 1622) there are 

 z 



