DEVELOPMENT OF PLANTS 147 



given by Linnaeus. So in other cases we can say white oak 

 or Quercus alba, scarlet oak or Quercus coccinea, etc. The oak 

 has several characters in common with the chestnut and beech- 

 nut genera, as for instance the fruit in each case is associated 

 with outgrowths that appear as the burr in the chestnut and 

 beech and as a cup in the oak. On account of these and other 

 common characteristics these genera are supposed to be related 

 and are therefore grouped together in one family. A family 

 is composed of allied or related genera. The name of the family 

 is derived from some characteristic genus in the group. In 

 this case it happens to be the beech or Fagus. To distinguish 

 a family from a genus the termination aceae is added to the base 

 of the generic word, in this example making the family name 

 Fagaceae. So we have the three allied genera, oak, beech, and 

 chestnut forming the beech family or Fagaceae. In the same 

 way it will be found that families are related and joined together 

 into a still larger group known as the order. The flowers of 

 the birch, alder, water beech, and hazel genera are very similar 

 and consequently form a family known as the birch family or 

 Betulaceae, Betula being the name of the birch genus. It will 

 also be noticed that there is a similarity between the flowers of 

 the Betulaceae and Fagaceae. This relationship is expressed by 

 placing them in the same order known as the beech or Fagales, 

 the termination ales being employed to distinguish the order just 

 as aceae characterized the family. So also orders are related 

 and grouped into classes. For example, the Fagales and many 

 other orders are characterized by having seeds with two cotyle- 

 dons. Several other orders have seeds with but one cotyledon. 

 This relationship is expressed by grouping the orders into two 

 classes, Dicotyledones and Monocotyledones. In both of these 

 classes the seeds are inclosed within the pistil, but in the cone- 

 bearing trees the seeds are exposed on a flat scale-like organ. All 

 seeds producing plants belong to one or the other of these two 

 groups. So we have two subdivisions, the Angiospermae, mean- 

 ing seeds inclosed, and the Gymnospermae, meaning naked seeds. 

 If now we stop to consider still larger groups than subdivisions, 

 it will be noted that many plants do not produce seeds, as in the 



