24 EASY LESSONS IN VEGETABLE BIOLOGY. 



found in a house, considered as a building. Let us 

 suppose that all kinds of houses may be referred to one 

 or other of three types, or general plans the Oriental 

 type with a dome roof, the Grecian type with a flat 

 roof, or the Gothic type with a pointed roof. We 

 select a house of the Grecian type. But there are 

 several classes of the same type, as made of wood, 

 iron, or stone. Our supposed house is a wooden one. 

 But there are several orders in each class. Thus 

 we may have Pine, Oak, Mahogany, etc. The house 

 we are considering is built of oak. In each order 

 there are other groups, or genera. The doors may be 

 at the front or at the side. Of the kind, or genus, 

 having the door at the front, there are more specific 

 kinds, according to the resident. In our supposed 

 case, the specific house is John Smith's. Thus, if we 

 have rightly classified we have learned that John 

 Smith's kind, or species, of house, is of the genus, or 

 group, which has front doors belonging to the larger 

 group, or order, of houses built of oak. This again 

 is grouped in the class of wooden houses under the 

 Grecian type. 



In a similar manner naturalists try to group to- 

 gether living things according to their real relation- 

 ships. All systems, however, are imperfect, on ac- 

 count of our imperfect knowledge, and we need not 

 be surprised to find one naturalist referring a form 

 to a group very different from that to which it is 



