On the Number of Chloroplasts in the Cells of the Sporophyte of Anthoceros laevis

Abstract

In a study of the morphology of the gametophyte and sporophyte of Anthoceros laevis L., the writer was somewhat surprised to find in stained microtome sections of the sporophyte the presence of but one chloroplast in cell, since in the literature one is given the impression that sporophyte cells contain regularly two chloroplasts (Campbell 'I8, pp. I21, 142, 597). Inasmuclh as the single chloroplast in cell of the gametophyte, in all North American species, seems to be an organ as permanent as the nucleus, it would be natural to suppose that the cells of the sporophyte mnight contain two chloroplasts, one being derived from the egg and the other from the sperm in the form of a very small primordium. Hofmeister, as early as I862, stated in regard to the number of chloroplasts found in the sporophyte that cells of the upper part of the young fruit [A. laevis L. and A. putnctatus L.] contain without exception two chlorophyll bodies; but that in the inner tissue of the stem fgametophyte] the appearance of two chlorophyll bodies is unusual. Campbell ('i8, p. I42) in describing the sporophyte of A. fusiformis and A. Pearsoni, says that there is a doubling of chloroplasts in the sporophyte, and specifically that each epidermal cell contains two large chloroplasts like that of the gametophyte. He refers also to Schimper ('85) as having lnoted that the chloroplasts double in the sporophyte of Anthoceros. The statement of Schimper (i1c. cit. p. 21) pertains to A. laevis. The spore-mother-cell shows regularly only one chloroplast. Therefore the presence of two chloroplasts in the vegetative cells of the sporophyte would be strange and not easily explained. Strasburger ('80) and Davis ('99) have traced the complete history of the spore-mother-cell and its two divisions to form the tetrad. Barring nuclear details, it is not at all difficult to observe all phases of the division of the spore-mother-cells in the fresh material, since the spores mature gradually and the sporemother-cells readily separate from other.