236 THE STORY OF PLANT LIFE 



flower in the centre. The stigma ripens first. The 

 anthers close in wet weather. The flowers are 

 pollinated by flies, but bees and wasps visit them. 

 The capsule opens elastically, expelling the seeds. 



In this group are numerous interesting types. 

 Many are poisonous, and several of economic import- 

 ance, as Jatropha, Manihot or Cassava (poison- 

 ous but rendered edible by heating), Hevea elastica 

 (rubber), Ricinus (castor-oil plant.) The real caper 

 plant, Capparis spinosa (Capparidacese) of the Mediterr- 

 anean region, which yields capers (the flower-buds) 

 is sometimes confused with Euphorbia lathyris, 

 common in gardens, but native only in woods. The 

 capsules, however, are poisonous. Poison for arrows 

 is obtained by the natives of Africa and America 

 from some exotic Euphorbias. Blisters are caused 

 by the Tirucalli, an Indian species. Gum resin is 

 obtained from some African species, the stems being 

 pierced as in the rubber trees for the juice or sap, 

 which is very poisonous. Pliny says it was called 

 after the physician of King Juba, Euphorbus. The 

 Mannicheel tree is said to be so poisonous that a 

 person sleeping under it dies, whilst a drop of the 

 white juice falling on the skin burns like fire. 

 Tapioca is the starch yielded by the Manihot. 

 Croton yields the cascarilla, a fragrant aromatic bark, 

 and oil is yielded by C. tiglium. The Box is 

 poisonous, and boxwood sawdust used in artificial 

 drying of flowers, etc., should be used only with 

 caution. The Dog's Mercury is also poisonous. 



