Imprints of domesticated pearl millet (Pennisetum glaucum (L.) R. Br.) spikelets, observed as temper in ceramics dating to the third millennium BC, provide the earliest evidence for the cultivation and domestication process of this crop in northern Mali. Additional sherds from the same region dating to the fifth and fourth millennium BC were examined and found to have pearl millet chaff with wild morphologies. In addition to studying sherds by stereomicroscopy and subjecting surface casts to scanning electron microscopy (SEM), we also deployed X-ray microcomputed tomography (microCT) on eleven sherds. This significantly augmented the total dataset of archaeological pearl millet chaff remains from which to document the use of the wild pearl millet as ceramic temper and the evolution of its morphology over time. Grain sizes were also estimated from spikelets preserved in the ceramics. Altogether, we are now able to chart the evolution of domesticated pearl millet in western Africa using three characteristics: the evolution of nonshattering stalked involucres; the appearance of multiple spikelet involucres, usually paired spikelets; and the increase in grain size. By the fourth millennium BC, average grain breadth had increased by 28%, although spikelet features otherwise resemble the wild type. In the third millennium BC, the average width of seeds is 38% greater than that of wild seeds, while other qualitative features of domestication are indicated by the presence of paired spikelets and the appearance of nondehiscent, stalked involucres. Nonshattering spikelets had probably become fixed by around 2000 BC, while increases in average grain size continued into the second millennium BC. These data now provide a robust sequence for the morphological evolution of domesticated pearl millet, the first indigenous crop domesticated in western Africa.

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In the circulating blood of anemic ducks, 5 % of all erythroid cells synthesize DNA. Immature erythroblasts, at all stages of differentiation, synthesize DNA although to a varying degree, while reticulocytes and erythrocytes do not. In the erythroid cell population labeled in vitro 2 h with 32Pi, half of the labeled DNA sediments as small-molecular-weight molecules, suggesting that these molecules fail to integrate into the high-molecular-weight components.Labeled DNA is found in the cytoplasmic postmitochondrial fractions and it is in a form of deoxyribonucleoproteins which cosediment with ribosomes as well as subribosomal particles in sucrose gradients. However, fixation with HCHO and centrifugation to equilibrium in CsCl gradient of these particles shows that the deoxyribonucleoprotein bands at the density different than the ribosomes and, thus, not physically linked to them. In EDTA-dissociated ribosomes, the deoxyribonucleoprotein particles cosediment with ribosomal subunits in such a way that the larger the particle, the larger the molecular weight of the DNA cosedimenting with it.The specific radioactivity of the cytoplasmic ribosome-derived and postribosomal-particlederived DNAs and the small molecular-weight nuclear DNA is similar and 10-20-fold higher than that of the bulk nuclear DNA. The former three DNA species sediment between 4-14 S. It is concluded that the cytoplasmic nonmitochondrial DNA species are of the nuclear origin. Less than 0.5 % of the total cellular nonmitochondrial DNA can be purified from the nucleus and the cytoplasm as fast-labeled small-molecular-weight components. All of the cellular nonmitochondrial DNA species band at the same mean buoyant density in Cs2S0,/urea gradients. All behave as native structures in hydroxyapatite and contain less than 5 "/, of their length as single-stranded regions. down product of the nuclear DNA. Furthermore, Fromson and Nemer [7] have attributed the presence of DNA in cytoplasmic nonmitochondrial fractions to contamination by a nuclear leakage. The problem, however, remains unsolved due to recent findings by Koch [8,9] that when compared to the nuclear DNA, the cytoplasmic DNA seems to be relatively enriched in unique sequences.The transfer of the products of transcription from the nucleus to the cytoplasm in the form of mRNA and its translation on ribosomes has been extensively investigated, for instance in avian erythroid cells [lo, 111. The primary transcription product of the globin genes is of the size 5 x lo6 daltons [12,13] and is suggested to be the precursor of the cytoplasmic mRNA (pre-mRNA). Although there is little doubt about the role of this pre-mRNA as intermediary in cellular information transfer, a straightforward scheme of direct

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