Among the nine hundred species of Solanum less than a dozen have this property of forming tubers, but similar growths are formed at the ends of the shoots of the common bramble, of Convolvulus sepium, of Helianthus tuberoses, the so-called Jerusalem artichoke, of Sagittaria, and other plants.
The Mount Vernon beds, which occur about the middle of the series, have as yet yielded only a small number of species, though these include the most interesting early Angiosperms. Among them are recorded a Casuarina, a leaf of Sagittaria (which however, as observed by Zeiller, may belong to Smilax), two species of poplar-like leaves with remarkably cordate bases, Menispermites (possibly a water-lily) and Celastrophyllum (perhaps allied to Celastrus).
Heterophylly is rather common among aquatic plants, and is well seen in several aquatic species of Ranunculus, many species of Potamogelon, Sagittaria sagittifolia, Scir pus lacusiris, Castalia (Nymphaea) alba, Hippuris vulgaris, Callitriche spp., Sium latifolium.