The Jepson Manual 

The Jepson Manual is a huge dichotomous key to native and naturalized plant species in California.

The key is broken up into sections.

• There is a key to families.
• Each family has a description of general characteristics of plants in that family and a dichotomous key to genera in that family.
• Each genus has a description of general characteristics of plants in that genus and a dichotomous key to species in that genus. (The key on the previous page was the key to species in the genus, Brassica.)

Some keys are so large that they are broken into 'groups' that then have their own keys. This is just to make the size of the keys more manageable.

Finally, there is a description of each species. This description gives the species' characteristics, its geographic range (where it is found in California), its elevation range, and the plant communities it inhabits. It also tells whether the plant is native or introduced to California.

 Here is an example of the description of Brassica nigra with links back to higher taxonomic levels (description and keys for the family and genus it is in).