Techniques for Collecting Aquatic and Marsh Plants

Abstract

Aquatic and marsh plants are those species occurring in substrates saturated with water most or all of the year. These substrates may be inundated permanently or may have the water table at the substrate surface. This habitat often poses a barrier to the collector and special problems in specimen preparation. As a result, aquatic and marsh plants are often inadequately collected and, therefore, poorly represented in herbaria. When collecting for aquatic or marsh species, I examine almost every wet spot, pool, lake, or stream I encounter and wade to the plants, if necessary. The substrate is often quite muddy and I may sink to the knees or deeper. When the water is too deep to wade, I prefer using a small boat and then dragging the substrate with a rake or grappling hook (one constructed from pipe ca. 20 cm long by 2 cm wide, coat-hanger, and rope ca. 10 m long is adequate). One can, of course, stand on shore and toss the grappling hook into the bed of plants, if the plants are fairly close. It is important to make complete specimens, including stems, leaves, roots, and reproductive structures-preferably mature flowers and fruits-of aquatic and marsh plants. Both staminate and carpellate flowers should be collected for taxa with imperfect flowers, e.g., Hydrocharitaceae.. Sterile specimens should be collected only for those taxa, e.g., Lemnaceae, that are so rarely seen in flower that the taxonomy is based upon vegetative features. Some persons believe that aquatic habitats are visited so rarely that it is better to collect a sterile specimen than none at all. However, if the specimen cannot be determined, it might as well be left in nature. Label data are especially important with aquatic or marsh plants. Information other than normal locality data that should be included are depth of water; flow rate of water; range of leaf size; whether leaves are submersed, floating, or emergent; color of flower; odor of flower; time of day of flowering; whether flowers are submersed, floating, or emergent; and whether fruits are submersed, floating, or emergent. Care must be taken to prepare quality specimens of aquatic vascular plants. They normally do not need to be pressed immediately following collection. I usually wrap each collection in dry newspaper and store these wrapped collections in plastic bags or styrofoam chests. These bags or chests are kept in the shade to prevent overheating the plants. The moisture from the specimens is adequate to moisten the newspaper and to keep the specimens fresh and pliable for several hours. The plants can be pressed later that day when one has ample time to do the task carefully. Several taxa, e.g., Heteranthera and Utricularia, have delicate flowers that are destroyed or from which the corolla falls offin the bag or press. Two or three flowers of these taxa should be preserved in 50% aqueous methyl or ethyl alcohol solution. Plastic 20 ml vials are excellent for this. Also, the duckweed press, which is discussed later, works well for pressing these flowers. Many species of aquatic and marsh plants have fairly large bulky stems, leaves, and subterranean parts. These large organs pose special problems when pressing. First, all parts of a specimen, other than the bulky structures, will have inadequate pressure in the press; as a result, they shrink during the drying process. This shrinking can be corrected by placing layers of newspaper on the flatter parts while the plant is in the press. Second, these bulky organs tend to have large amounts of water and, therefore, dry slowly-so slowly, in fact, they may completely decay while in the press. This decaying can be eliminated by splitting the large structures before pressing and by changing the corrugates and blotters of the press each day. Delicate aquatic plants, especially those that