Incomplete herbarium collections make it difficult to determine whether certain groups represent single species, or groups of similar species.

This problem is complicated by the fact that many of these species are poorly represented in herbarium collections.

A herbarium collection of over 5,000 specimens was started by the German-English Academy in 1852.

However, the herbarium collection increased and more time was directed to horticulture and botanical work.

After the initial description, a second herbarium collection was made in 1985.

Working from herbarium collections, De Candolle searched for general rules of plant distribution and settled on using temperature as well.

At first, the herbarium collection occupied one room at the cure Dutoit.

The herbarium collection was finally given its own home in 1964 with the construction of the current museum in the botanical garden of Lausanne.

His herbarium collections number more than 13,500 specimens, each with three to four duplicates on average.

Since 1855 the herbarium collection has been housed in five different places, and its botanical library in six.