50 Years Ago

The evolutionary origin of mitochondria, chloroplasts and kinetoplasts has recently been the subject of some intriguing speculation; several workers have suggested that these organelles have had an exogenous origin, perhaps evolving from symbiotic bacteria. These ideas stem from genetic evidence for the existence of extrachromosomal genes and the discovery that mitochondria and chloroplasts contain DNA and ribosomes and are capable of synthesizing proteins in vitro ... Although it is unlikely we shall ever be able to prove or disprove the hypothesis of the exogenous origin of these organelles, the fact that chloroplast and probably mitochondrial ribosomes differ from cytoplasmic ribosomes suggests that cells contain two independent protein synthesizing systems perhaps subject to different control mechanisms.

From Nature 6 May 1967

100 Years Ago

It is usually stated that the carat weight of jewellers and diamond merchants is derived from the hard seeds of the locust tree, Ceratonia siliqua, which were anciently used as weights. Having had occasion to obtain some of the beans, I weighed several of the seeds to see what sort of error would be incurred if they were used as weights ... It would appear ... that the carat weight could be recovered with some approach to accuracy by weighing a number of seeds of the locust bean. It is also evident that the use of such seeds as weights must have given opportunities for fraudulent dealing in the precious commodities gauged by means of them, since deviations of from 30 to 40 per cent. from the average may occur.

From Nature 3 May 1917 Footnote 1