MUTUAL CONNECTIONS OF PLANTS. 103 



either Tribes (tribm) or Families. Every person admits 

 that the different species of Grain, the Palms, Ferns, and 

 common Fruit-trees, are such Tribes or Families. 



155, 



But we distinguish these two ideas from one another in 

 •this way ; that by a Tribe we understand a smaller number 

 of related genera ; a Family^ again, denotes the sum of all 

 the genera, which agree in one or more essential parts : a fa- 

 mily may thus consist of several tribes. If, for example, we 

 assume all the species of Grasses as one family, then this con- 

 sists of the Hordeaceae, the flowers of which are placed on a 

 spike, — of the Avenaceas, which flower in panicles, and have 

 a twisted awn,— and so forth. The names of these tribes, as 

 the examples we have given shew, are commonly borrowed 

 from the principal genus, to which a termination is given, ex- 

 pressive of the resemblance. We hence say, the Cyperoideae, 

 Orchideas, Junceae, Aroideas, Jasmineas, Gentianeas, and so 

 on. We proceed, in the same manner, in giving names to 

 Families. But these are, with as much propriety, denoted, 

 usually, by general names, which have a relation to the prin- 

 cipal property. We thus derive the Ferns, Sarmentacea?, 

 Coronariae, Labiatae, Asperifoliae, Cruciatae, Compositce^ Ag- 

 gregatie, 



156. 



The laws which are followed in the construction of Gene- 

 ra, have the same importance in the establishment of Tribes 

 and Families ; for, fundamentally, the latter are nothing but 

 genera, and our only concern, therefore, is to separate them 

 from one another by constant characters, and to be able to 

 .mark out their connections with one another. 



