Ultrastructure of the sporophyte foot-gametophyte vaginula complex inTimmiella barbuloides (Brid.) Moenk.

The sporophyte foot of the mossTimmiella barbuloides consists of an unistratose epidermis of transfer cells, a parenchymatous cortex, and a small central strand consisting only of hydroids. The parenchymatous tissue of the vaginula develops one layer of transfer cells opposite the foot, whose lower extremity extends into the gametophyte stem's central strand. From the bottom to the top of the foot the ultrastructure of the sporophyte transfer cells shows some gradual changes that appear related to a functional specialization of these cells. According to a centripetal gradient, the quantity of plastid starch progressively lessens in both vaginula parenchyma and foot cortex. the observed morphological patterns suggest that in the foot-vaginula complex nutrients are translocated radially up to the sporophyte central strand.