A Spirit Collection of Vascular Plants at the Muséum National D'histoire Naturelle Herbarium

Abstract

During the completion of the 2006–2013 renovation project of the Muséum National d’Histoire Naturelle herbarium in Paris, all fluid-preserved specimens were transferred to three storage areas on the fourth floor of the botany building in the Jardin des Plantes. This fluid-preserved spirit collection includes ca. 15,000 jars containing vascular plants, mainly angiosperms collected since 1900, many of which are linked to additional specimens and preparations (herbarium sheets, wood samples, and DNA samples) stored elsewhere, such as in the actual herbarium. These fluid-preserved specimens are essential for thoroughly studying and illustrating succulents and pulpy fruits as well as for the floral morphology of some families (e.g., Orchidaceae or Zingiberaceae) and are thus often sampled and sometimes further processed by visiting specialists. They are also primary sources for other collections, such as the anatomical microslide library (“Histothèque”) for examining cytological details and the pollen slide library (“Palynothèque”). Maintenance and safety of the fluid collections were greatly improved by the addition of an extractor hood that made the practical work of fixation, preservation, rehydration, bottling, and rebottling of specimens easier. The use of effective fluids, such as the fixative FAA (formaldehyde 2%, acetic acid 5%, ethanol 67%, methanol 0.4%, water 25.6%) and the glycerol/ethanol/water mixture, along with standardized glass jars, greatly improved the storage and preservation of the specimens. While it is difficult to dispense with formaldehyde due to its good fixative properties (Buesa 2008) and its accordance with classical histological methods, it needs to be removed for health and safety reasons (e.g., it is carcinogenic and affects the lungs; see Goris et al. 1998) and to avoid long-term consequences, such as decalcification or pollen exine deterioration in preserved material. The use of any alternative to formaldehyde as a preservative fluid (Carter 2012) is a priority in collection areas such as algae but not necessarily for vascular plants and mushrooms. Histological studies may be carried out on dry samples after careful rehydration with dilute ammonia (5–10% aq.) or after heating at 60°C in heavily dehydrated tissues (Espinosa and Pinedo Castro 2018), recovering their original volume and outline but usually with clearing due to loss of tannins (Deroin 1994). Retrieval of preserved material in a continuously ventilated room (70 m3) is made easier by using three kinds of arrangements: unsorted field collections in stacking tanks, easily ordered arrays in chemical safety cupboards, and reference collections on shelves, free or in glass cupboards or drawers. The reference collections fulfill different aims. Some of the specimens in this collection are reserve vouchers for phytogeographical and ethnographic exploration, such as Léon Diguet’s samples of the useful Cactaceae fromMexico gathered in 1902–1904 (Fig. 1A–C). A book was published posthumously (Diguet 1928), giving numerous and detailed comments that enhance this reference collection, which is most likely to be used in temporary