ИСТИНА

Osmundaceous macro- and microremains are common in fossil state since the Late Permian. Spores of modern Osmunda regalis L. and O. vachellii Hook. were collected from slightly immature sporangia and studied with LM, SEM, and TEM. Spores of both species are similar, trilete, spheroidal, 50-60 µm in diameter. Laesurae are thin, 15-23 µm long. The surface is pitted-verrucate, with the verrucae of about 2 µm high. Distally, they are high, bearing smaller verrucae and rodlets. Proximal verrucae are smaller, slightly variable in sizes and outlines. The perispore is electron-dense, thin, interrupted, granular, and forms rodlets. The exospore consists of three layers in the area of the proximal scar and of two layers in non-apertural regions. The outer exospore is thick, vaguely layered, and forms verrucae. Innerwards, the outer exospore gradually becomes less electron-dense. The inner exospore is thin and electron-translucent. Occasionally, narrow gaps are visible between the outer and inner exospores filled with electron-dense content. The exospore becomes three-layered in the area of the proximal scar. The outer exospore does not differ from that of non-apertural regions. The middle exospore is thick, more electron-dense than the outer and inner exospores, layered along the laesura, with small lense-like cavities. The pseudoexospore is thin and electron-translucent. My data agree with data by Tryon and Lugardon (1991). Apart from intact spores, I have also studied acetolyzed spores of O. regalis and O. vachellii from sporangia, which were situated symmetrically on the same pinnules. For comparison, I observed acetolyzed spores of the marattiaceous Angiopteris yunnanensis Hieron., A. polytheca Tardieu et C. Chr., A. palmiformis (Cav.) C. Chr., and Marattia sp. from the greenhouse of the Komarov Botanical Institute of the Russian Academy of Sciences. Unlike the Marattiaceae, the acetolyzed sporoderm ultrastructure of the Osmundaceae is very peculiar. The perispore and pseudoexospore did not survive acetolysis. The outer exospore shows wave-like layering. It is electron-dense, gradually wading out at the apices of the verrucae. Innerwards, the waves become smaller and less electron-dense. The inner exospore is electron-dense and contains slit-like cavities. In the area of the proximal scar, the outer and middle exospores are wave-like; there are cavities in the middle exospore. The inner exospore is thin, electron-translucent, and homogeneous. In acetolyzed spores of the Marattiaceae, the outer exospore areas that form the sculptural elements become electron-translucent, maculate, or granular; however, I have not detected wave-like patterns. I hypothesize that the wave-like pattern is detectable in the exospore in fossil state, that can be helpful for more reliable identification of dispersed osmundaceous spores.