A Monograph of the Fern Genus Pyrrosia (Polypodiaceae)

Abstract

In addition, living plants were studied from appr. 20 species cultivated in the Leiden Botanical Garden. Methods and techniquesIndument Rhizome. The scales of the rhizome were wetted with a strong solution of photographic detergent (KODAK : waterappr.1 : 3), then lifted from the rhizome. In order to obtain whole scales it is sometimes necessary to dissect carefully as the scales break off easily above the point of insertion. The scales were then rinsed in water and semi-permanent preparations were made by embedding them in glycerin-jelly.Fronds. The hairs on the stipe and lamina were treated in a similar way, but careful dissection is not necessary here. Anatomy Rhizome, stipe. For anatomical study pieces of rhizome or stipe were boiled in water, usually after adding a few drops of detergent (see above), for a few minutes, or until they sank when transferred to cold water. They were sectioned at ± 30 pm with a Reichert slide microtome using a Gilette double-edged razorblade. The sections were embedded in glycerin jelly. No staining or other treatment of the sections was found to be necessary to study the distribution of the vascular strands and/or the sclerenchyma.Rhizome scales. Cross-sections through the rhizome scales were often found to be included in cross-sections of the rhizome. Thinner sections were prepared 4 by boiling the scales in water for several minutes and then sectioning the softened scales at 5-10 (xm using a slide microtome with a double-edged razor blade and elder-pith. Sections of scales obtained in this way were found to be superior to sections obtained after embedding the scales following routine procedures.Lamina. Cross-sections of the lamina were prepared in a similar way as those of the rhizome (see above) but were sectioned at 20-30 pm. The sections were bleached in a commercial solution of hypochlorite, stained for a few minutes in Astra-blue, and embedded in glycerin jelly. To obtain epidermis peels, as a rule small pieces of lamina were bleached following a procedure slightly modified from that used for studying the venation (see below). They were simply boiled in a 5 % solution of KOH, then bleached in hypochlorite. Either the lamina in its entire thickness was then embedded in glycerin-jelly, or the mesophyll was scraped away as much as possible. Staining with Astra-blue was sometimes applied. Due to the diversity in anatomical structure of the lamina the results thus obtained were highly variable in quality. More conventional methods of obtaining epidermis preparations by maceration were found to yield equally unsatisfactory results and are more laborious. VenationFor study of the venation sufficiently large pieces of lamina were cleared following the procedure developed by O'Brien & Von Teichmann (1974). This involves autoclaving the pieces in a 5 % solution of KOH and then bleaching them in commercial hypochlorite. For Pyrrosia this was found to yield better results than bleaching with chloro-lactophenol according to Hennipman (1977).Unfortunately, after the treatment the tissu...