226 



IMPORTANT FAMILIES OF PLANTS 



shell bark, and //. olivcuforinis, 11. pecan, the pecan of com- 

 merce) are well known for their nuts and useful woods. 



Propagation. — The members of this family can be grown 

 from seeds or by grafting. The fact that seedlings are subject 

 to more or less variation makes it necessary to perpetuate de- 

 sirable varieties by grafting, which must be done with consid- 

 erable care in order to be successful. 



FlQ. 148. — Pecan nuts, showing one of tho many forms grown for market. (U. S. D. A.) 



OAK FAMILY (CUPULIFER^) 



This family is similar to the preceding. The flowers are 

 monoecious. The staminate flowers in catkins, calyx five-parted 

 (occasionally five to twelve), stamens two to twenty. The pis- 

 tillate flowers terminal, six-parted, and attached to the two- to 

 seven-chambered ovary. Fruit a one-seeded nut. This family 

 includes the oaks, chestnut, hazelnuts, beech, and others. 



There are many species of oaks (Quercus) which are among 



