Certain marine algae were treated with sea water containing carrier-free radioactive strontium (mixture of Sr89 and Sr90), to test whether these ions were taken up by the weeds.

At the same time the behaviour of radioactive yttrium (Y90), which occurred as a short-lived daughter-product of Sr90, was investigated by the expedient of studying the ‘decay’ characteristics of specimens of water and weed.

Promising possibilities of this technique, by which an isotope is made available for study by applying its parent substance, are pointed out.

Radioactive strontium is extracted from sea water by the brown sea-weeds, in particular by Fucus serratus.

It is held that this effect is simply a result of ionic exchange, and that the algae regularly contain many times as much strontium in their cell fluids as exists in sea water.