 Most herbaceous plants are dug up with a little soil on the roots. Some botanists had the habit in the time when a lot of the collecting was being done of washing the roots, but others didn't and those where they didn't wash, the soil can be used for pollen analysis to tell what the sort of climate was where that plant grew by looking at the whole complex, not just the one plant, but the whole complex that the pollen indicates was there. And there have been such studies. Another thing that we're now doing is there are some herbarium specimens that represent specimens of trees which are still alive and maybe the specimen was collected 100 years ago and the tree is still alive and it's interesting to look at what the difference is between the pollen and the living tree and what it was like 100 years ago. There are differences and some people think it is due to increase in air pollution or possibly it's just mutations but there is a difference and it's interesting to study.