On the collecting and preparation of Utricularia specimens

The taxonomic study of this genus is, and always has been, severely hampered by the almost universal incompleteness of the material available in the herbarium. The vast majority of herbarium specimens, at least of the terrestrial species which comprise some 70% of the genus, consist of inflorescences alone, i.e. without vegetative parts. The aquatic species fare little better and although specimens are often more complete they are usually badly prepared so that vital characters such as the specifically characteristic branching of the foliar organs is completely obscured. Furthermore, in view of the very delicate nature of both the floral and vegetative parts, especially the complex and often very small traps, drying is rarely as satisfactory as preservation in liquid. This latter method, which has been increasingly used in recent years, can however produce relatively useless specimens if the incorrect liquid preservative is used. Having personally collected some 25% of the 180 known species both in Europe and the tropics of Africa and America the author feels qualified to offer some advice on the preparation of specimens of this genus for taxonomic study. 1) Dried specimens — Aquatic species should be put into a suitable receptacle (at least 0.5 m square) full of clean water about 15-20 cm deep. Gentle agitation will cause the vegetative parts to assume their natural position. A sheet of paper, either thin and suitably supported on a rigid sheet of metal or thicker and unsupported, is then carefully introduced beneath the floating plant and very gradually raised out of the water so that the plant eventually lies on the paper with all of its parts in their natural positions. The whole should then be dried as rapidly as possible in a ventilated press. Additional separate inflorescences (and infructescences) may of course be dried normally. Terrestrial species often have no very obvious vegetative parts as they are usually beneath the substrate. However it is the experience of the author that they are in fact almost always present and may be found by carefully removing a small piece of the substrate with the inflorescence. Gentle agitation in water may wash away the sand, soil or mud and these vegetative parts are again best displayed by ’floating out’ as for the aquatic species. If, as is frequently the case, the substrate is bound together by filamentous algae or the subterranean parts of other plants, the vegetative parts are difficult to separate and display, at least in the field, and in such cases the whole should be pressed.