Sentence:  With fresh material, taxonomic conclusions are leavened by recognition that the material examined reflects the site it occupied; a herbarium packet gives one only a small fraction of the data desirable for <WSD>sound</WSD> conclusions. Herbarium material does not, indeed, allow one to extrapolate safely: what you see is what you get... 
Meaning of the word marked with <WSD> tags:  Having the property of soundness.