Pohlstoffe, a Good Wetting Agent for Bryophytes

Abstract

The agrostologist, Pohl, suggested the use of a wetting agent based on di-octyl sodium sulfosuccinate. It has proven very useful for the study of bryo- phytes, with certain reservations when applied to living specimens of the Hepati- cae. Pohl (1965) published a short note outlining methods for handling difficult dissections of grasses. Several of his recommendations are worthy of wider adoption by bryologists. His suggestion that the most useful tool for dissections is a well-cultivated fingernail remains valid. The formula for a wetting agent, known as to its aficionados, is par- ticularly effective in bryological applications. The wetting agent, di-octyl sodium sulfo- succinate (brandname: Aerosol OT, available from Fisher Scientific Company) is mixed with methanol and water in the ratio 1:24:75. A modification of Pohlstoffe, omitting the methanol and crudely measuring the wetting agent (ca. /4 dropper full per dropping bottle of distilled water), produces a solution with remarkable advantages over plain water or water with other detergents. Most dried mosses absorb Pohlstoffe almost instantaneously and spring back to turgidity. The ease with which dry capsules and peristomes are wetted eliminates the need to heat slides over a lamp. The reduced surface tension causes the water to evaporate fairly rapidly, making it unnecessary to return soggy specimens to the packets. No detectable residue remains on the specimens. If protracted dissections are required, the specimen may be re-wetted with plain distilled water which will penetrate rapidly but evaporate more gradually. Likewise, water mounts under coverslips to be kept for any length of time should be made with plain distilled water or replaced with glycerin, Hoyer's, or other more permanent mediums. Pohlstoffe works equally well with dried hepatics, excepting those thallose species which never satisfactorily regain life-like form. It should be noted that use of Pohlstoffe on hepatics must be avoided when one wishes to examine oil-bodies. The wetting agent in Pohlstoffe causes a distressingly rapid dis- integration of the oil-bodies; patience and plain distilled water must be relied upon when dried (but still living) specimens of hepatics are examined. Pohl, R. W. 1965. Dissecting equipment and materials for the study of minute plant structures. Rhodora 67: 95-96.