From Audrey Berrie
Chlamydomonas nivalis, the “watermelon snow” described by Lisa Grossman in her article on extreme life (14 June, p 13), is not a type of red algae but a green alga in the Chlorophyta phylum. As well as the usual green pigment chlorophyll, it has an additional carotenoid pigment, giving the algae its red colour.
Torquay, Devon, UK
