Vascular Herbarium

Holdings of vascular plants at PH include >1 million specimens, the vast majority of which are mounted and stored conventionally. Pandanaceae are the crown jewel of our boxed / bagged collection of cones, fruits and seeds. These plants are the "screw pines," a group of woody Old World plants that look a bit like palms. As a result of Ben Stone’s tenure here as curator, PH holds a remarkable series of infructescences, seeds, stems and occasionally other structures of screw pines.

It is both frustrating and exciting that it is so difficult to decide upon the best system for filing specimens of vascular plants in a modern herbarium. Frustrating because there is yet no fully resolved, strongly supported single phylogenetic system for these plants. Exciting because we have made a great deal of progress toward such a system. The good news is that we know a great deal more about the relationships of seed plants than we knew a very few years ago. The bad news is that this progress has served in part to point out the problems with all existing systems.

Why worry about filing phylogenetically at all? If you like to browse in libraries (or even in the grocery or hardware store), you will already know the answer. If you are seeking a particular book on a particular topic, it is interesting and often highly rewarding to encounter other books on this topic (rather than books by authors whose names happened to be alphabetically proximate to your original target book). Similarly, imagine a grocery shelf with beets next to bird seed next to chamomile tea… you’d rather have beets with the other canned vegetables, bird seed with the pet foods, etc., right?

We are currently filing seed plants by a system based on Dalla-Torre and Harms (ca. 1890) with a number of modifications designed to make our system better reflect what we know about plants. This system is certainly far from perfect and will no doubt be further modified. At the same time, progress is being made quite quickly in resolving some of the issues about plant relationships that we need to resolve in order to achieve some degree of both stability and accuracy (see, for example, the terrific Angiosperm Phylogeny web site maintained by Peter Stevens).

At PH, you will find our current system posted prominently in numerous places arranged both alphabetically by family and numerically (i.e., by numbers as assigned to families). Within families, genera are alphabetical and species are alphabetical within genera.

As we are in the process of implementing this system, you will find some families still filed by our older system. In all cases, if you do not find what you expect to find, ask a botany staff person for help.

Pteridophytes (i.e., ferns and fern allies) are the exception. Following the advice of our colleagues who study these plants, we are filing them alphabetically by genus (and alphabetically by species within genera).

Geographic Sources

Geographic composition of the Vascular Herbarium
Region %
Local (=southeastern PA and adjacent counties in NJ, DE and MD) 29%
Other Nearctic 41%
Neotropical 9%
Palaearctic 7%
Tropical SE Asia * 5%
Temperate East Asia * 3%
Other 6%
* Significant portions of our back-log, estimated at 97,000 are from these areas.

About 70% of our specimens are from North America, with an emphasis on Pennsylvania, New Jersey and Delaware. Research for two major recent publications on the Pennsylvania flora was centered at the herbarium (A.F. Rhoads, W.M. Klein, and J.E. Klein [1993], Vascular Flora of Pennsylvania: Annotated Checklist and Atlas and A. F. Rhoads, T.A. Block, and A. Anisko (Illustrator) [2000] The Plants of Pennsylvania: An Illustrated Manual. More information can be found at the website for the Pennsylvania Flora Project.