1982 Volume 52 Pages 465-499
The results of an ultrastructural study on the female gametophyte stem and sporophyte of Buxbaumia piperi Best are reported and discussed. The gametophyte stem consists of large and highly vacuolated parenchymatous cells rich in lipid reservoirs. The gametophyte plastids are very small, lack starch, and have a rudimentary lamellar apparatus. There are several layers of transfer cells on the gametophytic side of the placenta, but only one on the sporophytic side. Both the sporophyte foot and the seta are composed of an outer and an inner parenchymatous cortex, and of a small central strand of only hydroids. Because of the presence of an extensive lacunar system in the inner cortex, the seta structural pattern appears to be fundamentally like that of the polytrichaceous mosses, although leptoids are lacking in Buxbaumia. In spite of the great reduction of the conducting tissues, the sporophyte of Buxbaumia is complex in structure at both the histological and ultrastructural level. In particular an unusual plastid diversification has been observed in the various tissues. It is proposed that this may be related to the presumed antiquity of the taxon.
