THE PYRENOID OF ANTHOCEROS

Abstract

The single chloroplast of the cells of the gametophyte of the Anthocerotes, with its pyrenoid-like central region, has long been known. Notwithstanding this, detailed descriptions of these chloroplasts and pyrenoids and comparisons with those of the algae, on the one hand, and with the chloroplasts of the liverworts on the other, seem to be lacking. As early as I85I von Mohl (I4) called attention to the fact that there were wohl 50 bis IOO Amylumk6rner in the chloroplasts of Anthoceros, but he did not relate them to the starch aggregations to be found in the green algae. The voluminous earlier literature on the morphology of Anthoceros, as far as I can determine, contains only bare mentions of the chloroplasts and pyrenoids. Leitgeb (g) in fact seems to have made no reference whatever to these structures. Schimper (i8) states that the pyrenoids of Anthoceros zeigten nach Entfernung der Starke durch Verdunklung nur noch corrodierte, unregelmassig eckige Umrisse. His figures I5 and I6 are apparently surface views of entire, living cells and show only diffuse central regions which have no resemblance to the plastids as seen in stained material. Davis (5) in an account of the nuclear division and the fission of the chloroplasts in the spore mother cells of Anthoceros laevis makes no reference to a pyrenoid and nothing in his figures suggests such a structure. He is unable to identify plastids in the archesporial cells and only as these cells become spore mother cells can the single, very minute chloroplast be identified. This chloroplast enlarges rapidly and undergoes two fissions, thus forming the four chloroplasts of the spore tetrad. The large chloroplasts of the mature spores are filled with conspicuous starch grains, becoming thus storage vesicles of starch. Campbell (3, 4) has made the most important recent contribution