Sentence:  Swadesh , and therefore Hoijer , felt compelled to omit all terms denoting species or even genera ( fox , vulture , salmon , yellow pine , manzanita ) ; their <WSD>classes</WSD> of animal and plant terms are restricted to generalizations or recurrent parts ( fish , bird , tree , grass , horn , tail , bark , root ) . 
Meaning of the word marked with <WSD> tags:  a collection of things sharing a common attribute