Origin and structure of Ubisch bodies in Pinus sylvestris

In <em>Pinus sylvestris</em> Ubisch bodies are produced repeatedly, and each crop is formed at a distinct phase in the secretory cycles of tapetal cells. While each production has a Ubisch body wall similar to the then current state of the exine with regard to thickening and ornamentation, the survivers of previous productions do not change. Examples of all the structurally different Ubisch body wall forms can be seen when terminally, at the time of pollen shedding, the relict Ubisch bodies become spatially concentrated on the minimal surface area of the senescent cells of the tapetum. In angiosperms after one or a few periods of initiation Ubisch bodies may remain in association with the surface of tapetal cells where the Ubisch body wall undergoes changes like those of the maturing pollen exine. We conclude that as a consequence of Ubisch body detachment from the plasma membrane of tapetal cells there is in <em>Pinus sylvestris</em> no updated information for modification of the wall and the Ubisch body wall remains static.

A fossil flower with in situ Pistillipollenites from the Eocene of British Columbia

A single actinomorphic flower has been found in the Horsefly Mine Top Section (Middle Eocene) of British Columbia. The flower, 2.1 cm in diameter, has six sepals, probably a superior ovary, and six stamens, one opposite each sepal. The pollen is morphologically identical with that of the dispersed grain of Pistillipollenites macgregorii Rouse. Grains, 22 μm in diameter, have numerous gemmae supported by columellae and a finer ornamentation of nanoverrucae. The grains are triporate with gemmae around apertures. Spherical hollow Ubisch bodies indicative of a secretory tapetum underlie remains of tapetal membranes. The floral structure of this new taxon, Pistillipollianthus wilsonii gen. et sp. nov., is distinctly different from the only other Pistillipollenites-producing flower described from the Eocene of Texas. The current study indicates that Pistillipollenites grains identified in sediments from the Cretaceous to the Eocene probably represent pollen from different angiosperm families, and it adds to the evidence that this type of gemmate grain may have evolved several times through convergent evolution.