390 SYSTEMATIC BOTANY. 



find that some of tliera also resemble one another more than they 

 do others. Thus Mustards, Turnips, Eadishes, and Cabbages, 

 have a strong common resemblance, while they are unlike Straw- 

 berries and Brambles ; and even less so to Hazels, Oaks, and 

 Beeches ; and still more imlike Larches, Pines, Firs, and 

 Cedars. Proceeding in this way throughout the vegetable 

 kingdom, we collect together allied genera, and form them into 

 groups of a higher order called Orders or Families ; hence, 

 while genera are collections of related species, orders are col- 

 lections of allied genera. Thus Mustards, Turnips, Eadishes, and 

 Cabbages, all belong to dilFerent genera, but they all agree in 

 their general structure, and are hence included in the order 

 Cruciferse ; while Strawberries, Brambles, Cinquefoils, Eoses, 

 Apples, Plums, and Almonds, are all different genera, but from the 

 general resemblance they bear to one another in their structure, 

 they are placed in one order, called Eosacese. Again, Oaks, 

 Beeches, and Hazels, are different genera, but they belong to 

 one order ; also the Larches, Pines, and Cedars, are different 

 genera, but they all have a fruit called a cone, and are hence 

 placed in one order, the Coniferse. 



"We find also that certain genera of an order, like certain 

 species of a genus, have a more striking resemblance to one 

 another than to other genera of the same order ; hence such are 

 grouped together into what are called Sub-orders. Thus the 

 Chicory, Dandelion, Sowthistle, Lettuce, Thistle, Burdock, and 

 Chamomile, all belong to the same order, but there is a greater 

 resemblance in the Chicory, Dandelion, Sowthistle, and Lettuce, 

 to one another, than to the remaining genera. Hence, while all 

 the above genera belong to the order Compositse, they are at the 

 same time placed in two different sub-orders. Thus the sub- 

 order Liguliflorai includes the Chicory, Dandelion, Sowthistle, 

 and Lettuce ; and the sub-order Tubuliflorse, that of the Thistle, 

 Burdock, and Chamomile. In like manner, while we find the 

 Almond, Cherry, Strawberry, Easpberry, Eose, and Apple, all 

 belonging to the same order Eosacese, yet some of them have 

 more resemblance to one another than to others. Thus the 

 Almond and Cherry have a drupaceous fruit, and belong to a 

 distinct sub-order, which is called Amygdalese; the Strawberry, 

 Easpberry, and Eose, are much more like each other than they 

 are to the Almond and Cherry, or to the Apple, hence they are 

 placed in a sub-order called Eoseee ; while the Apple is placed 

 in a sub-order termed Pomese. 



It is found convenient at times to subdivide sub-orders 

 into Tribes and Sub-tribes, by collecting together into groups 

 certain very nearly allied genera, but it is not necessary for ns 

 to illustrate such divisions further, as the principles upon which 

 they depend have been now sufficiently treated of. 



