[Autoradiographic investigation on the transport of organic material in Polytrichum commune]

After application of 2 μc bicarbonate-(14)C on a single leaf of the gametophyte of Polytrichum commune L., labeled organic material moves upward with a velocity of at least 32 cm per hour. Historadiographs of transsections showed that radioactivity occurs in the leptoids of the stem and in certain cells of the leaf bundle, mainly the so called Socii. Hydroids and ground tissue of the stem remain unlabeled. One of several labeled organic substances found in the extract of leaves could be identified as sucrose. Gross autoradiographs of fresh plants were obscured by (14)C-contaminated capillary water, which had spread on the surface of the plant. This effect could be prevented by drying off the surface water. In Polytrichum, there seems to exist a special conducting system for assimilates, composed of leptoids and certain Socii. Both cell-types agree in shape and content. They have relatively dense protoplasts containing chloroplasts; the transverse end walls are commonly covered by a thin layer of callose. A cytologic and ultrastructural study is in preparation.