EXOGENS. 145 



ter is removed by heat or washing, and the starch is 

 used as Cassava bread. Tapioca and Brazilian Arrow- 

 root are said to be procured in this way. 



In the NETTLE family are about six hundred species, 

 including the common Nettle, Hemp, Hop, Elm, Fig, 

 Mulberry, Bread-fruit, the Banyan, (Ficus indica^) etc. 



The Catkin-bearing family (AMENTACE^) is the larg- 

 est and most important of this order, since it contains 

 all the most important timber trees. (Fig. 61.) The 



Alder, Birch, Willow, Poplar, Oak, Chestnut, Hornbeam, 

 and Plane are here brought together because of the simi- 

 larity of their fructification. They produce flowers of one 



sex only, the males of which are in catkins, in which the 

 13 



