[The submicroscopic structure of the assimilate conducting cells of Polytrichum commune]

In the young part of the stem of Polytrichum commune the protoplasts of the two types of conducting cells, the leptoids and parenchyma cells, are nearly identically equipped with cell organelles and cytoplasmic structures. Both types contain a nucleus, chloroplasts, mitochondria, and dictyosomes. The endoplasmic reticulum builds characteristic cisterns in form of hollow cylinders extending from one end wall to the other. The cisterns are connected with many plasmodesmata, which occur only in the end walls. Leptoids have oblique end walls with 16 to 20 plasmodesmata per μm(2), and parenchyma cells show cross walls perpendicular to the axis with 9 to 12 plasmodesmata per μm(2).Since the leptoids are supposed to be the pathways for the longitudinal transport of assimilates (ESCHRICH and STEINER, 1967, 1968), it is of interest that early in their development these elements undergo a change in their protoplasmatic structure. Two to 3 cm below the apical cell the protoplasts degenerate and show lysosome-like structures. The endoplasmic reticulum and other structures are deformed or dissolved; the plasmodesmata are constricted by callose deposits. At the same level the parenchyma cells still retain the original structure of their protoplasts.Thus, assimilates moving upward in one row of leptoids may penetrate the whole lumen of the leptoids at lower levels, but they are restricted to the cisterns of the endoplasmic reticulum at higher levels of the stem.

[The occurence and distribution of volatile amines in marine algae]

Twenty-eight species of marine Chlorophyceae (5), Phaeophyceae (11), and Rhodophyceae (12) were examined for the occurence of simple volatile amines. The volatile alkaline constituents of the algal samples were extrated by alkaline steam destillation and separated and identified by paper chromatography and microcristallography. A total of 9 volatile amines were found to occur in the species so far examined: methylamine (MA), dimethylamine (DMA), trimethylamine (TMA), ethylamine (ÄA), propylamine (PA), isobutylamine (iBA), isoamylamine (iAA), 2-phenylethylamine (PÄA), and 2-methylmercaptopropylamine (MMPA). MMPA has not previously been reported to occur in any other plant. The occurence of TMA is widespread in marine algae (23 of 28 sp.) whereas an occurrence of DMA could be demonstrated only in two species. MA, which was found in all algal samples, might be formed from labile methylamino-compounds in the course of preparation. Its coccurrence as a natural constituent of algae remains doubtful. Primary amines could be identified in species of each of the three classes of algae, but an especially widespread occurrence was found in Rhodophyceae. With the exception of MA the primary volatile amines, at least those of Rhodophyceae, arise biosynthetically from the corresponding amino acids by enzymatic decarboxylation.

[The structure of the conducting system of Polytrichum commune]

In a previous paper (ESCHRICH and STEINER, 1967) we could show that (14)C-labeled assimilates moved in the leptom cylinder of the stem of Polytrichum commune with a velocity of at least 32 cm per hour.The present paper deals with the structure and differentiation of the conducting system of the same species.The central core of hydroids, the water conducting tissue, is surrounded by the leptom cylinder. Embedded in this cylinder of parenchymatic cells are 8 longitudinal strands of leptoids, which are supposed to be the conducting cells for the long distance transport of assimilates. Leptoids differ from parenchyma cells in having oblique end walls. The leptoids originate from derivatives of the apical cell and differentiate in a basipetal direction.Leaf traces are composed of water conducting central cells, which are surrounded by parenchymatic cells, the socii on the abaxial side, the deuter on the adaxial side. A leaf trace entering the stem mostly contains 11 rows of central cell. Along the path of the leaf trace through the ground tissue to the axial conducting system, all central cells are eliminated except the middlemost cell, which eventually merges with the hydroids. The parenchymatic cells of the leaf trace are successively taken off by the ground tissue or they are eliminated. At the level with 4 central cells the leaf trace is devoid of socii and the remaing deuters may be connected with one or two leptoid strands by a group of cells, which is named leptoid bridge. The deuters and the cells of the leptoid bridge have the same oblique end walls as the leptoids.The whole structure shows that there exists only a loose connection between the axial conducting system and the leaf traces.

[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.