Making an identification: recommendations for using the APPW key.
The highly polymorphic growth development of aquatic plants makes them difficult to separate into exclusive categories; plant morphology may be different depending on the particular growth stage, or on environmental influences. The scoring of genera in this key has taken this polymorphism into account.
When using the key, the guiding principle can be: if your specimen looks like a leaf or stem or like it has leaves or stems, then you can use the leaf and stem features to identify it. Some plant groups are considered by some not to have true leaves (e.g. duckweeds and mosses), and some groups are not plants and do not have leaves (or roots or stems) (e.g. algae). In this key, however, taxa with organs that look like leaves or stems are scored so that regardless of whether you think a taxon has leaves or stems, or you know a taxon well and know, e.g., that it does not possess true leaves, you will be able to identify it.
The features are grouped into several Subsets that enable you to view e.g., only vegetative features or only leaf features, if, for example, you have only bunches of stem and shoot cuttings.
The drawings and photos used to illustrate feature states in this tool are just examples, or are diagrammatic, intended to be representative of a range in appearance. Your specimen need not look exactly like a state illustration; pick the state that, by its wording, best describes your specimen, or choose the state to which your specimen looks the most (not necessarily exactly) similar. Also, be sure to consult the explanatory text on the feature page.
An identification is easiest and most likely to be made if both vegetative and floral features are used. If floral features are not available on your specimen and you are using only vegetative features, some genera may be difficult to separate. Closely related genera in the families Alismataceae, Lythraceae, and Scrophulariaceae, for example, may not key out to one taxon unless floral features are used. In these cases, where a diagnosis is not possible based solely on the vegetative features available, once you have a short list of taxa in Entities Remaining, and are not be able to reduce that list further, you may very likely be able to make an identification by perusing the images and descriptions on fact sheets and image pages.
Many of the genera are quite morphologically variable. Be sure to look at all the images available on fact sheets and image pages, and not just at the images or image thumbnails attached to the taxa in the interactive key; for most of the taxa, fewer images are attached to taxa than are available on the fact sheets and image pages. Additionally, if in the interactive key you choose to view the image thumbnails and the entities as trees or lists, you will see only one thumbnail for each taxon in the Entities panels. This one image does not represent the whole taxon.
New introductions to the hobby and hybrids of established species may not easily key out. In this and other cases it is recommended that you confirm your identification by perusing the accompanying fact sheet and image gallery for the taxon and check out the links to fact sheets for taxa with which it could easily be confused. Remember, the aquarium and pond plant industry is constantly in flux, responding to changing customer needs and constantly introducing new species, cultivars and hybrids to the hobby. If an identification is not possible, then your specimen could conceivably be one of these new introductions to the hobby.
Review the best practice guidelines for further, comprehensive recommendations about how best to use Lucid interactive keys.