Morphology and Ultrastructure of Four Pennsylvanian Prepollen Types

Bisaccate Pollen of Probable Gnetalean Species and Pollen Diversity in Gnetophytes

“…The sacci are small and look like foldings of the exine. Similar structures were documented for some dispersed pollen grains (e.g., Zavada & Dilcher 1988) and for in situ prepollen of the seed fern Parasporotheca (Millay et al 1978, Taylor 1982. The infratectum is different in these findings including granular and alveolate types (Zavada & Dilcher 1988, Tekleva & Krassilov 2004.…”

The Okmulgee, Oklahoma fossil flora, a Mazon Creek equivalent: Spatial conservatism in the composition of Middle Pennsylvanian wetland vegetation over 1100km

“…Monoletes-type prepollen were found in these organs, overlying the interior portions of the lobes, from base to tip, but without evidence of the sporangia in which they were originally borne; the prepollen were monolete and fusiform in shape. Millay et al (1978) found the prepollen to average 329 μm × 233 μm. Drinnan and Crane (1994) found there to be a single, elongate, segmented sporangium running the length of each lobe, displaced toward the interior.…”

“…Darrah (1969) agreed with this interpretation. Certainly, the attribution of this organ to the medullosans is widely accepted based on its morphology and that of the pollen grains it contains (Wieland, 1924;Millay et al, 1978;Millay and Taylor, 1979;Stidd, 1981;Mapes, 1982). It also is noteworthy that these pollen organs often are massed, suggesting (perhaps seasonal) synchroneity of production on the parent plant, and possible attachment in groups (Plate X,(5)(6).…”

The ultrastructure of fossil gymnosperm pollen

“…7), or grana. ln sorne species, a thin nexine has been reported (Millay, Eggert and Dennis, 1978), white in others (C.…”

“…On the surface of the grain, the sexine forms a series of convolutions that give the surface a ridged ornamentation. On the distal surface is a small unornamented oval area where the nexine in thinner (Millay et aL, 1978).…”