Department) have been investigating the palaeoenvironments of eastern Lesotho through the use of pollen, diatom and sedimentary records.

In a case of 'accidental science', the group discovered the pollen of Chrysocoma cilliata at intermittent locations throughout the depth of the sediment profile they were studying. This was unexpected, as Chrysocoma ciliata is believed to be an invasive species introduced to the eastern Lesotho Highlands by cattle herders at the turn of the 20th century. The species was found to extend much further back in the pollen record than the 100 years that it is believed to have been growing in the region.

Chrysocoma cilliata came to the attention of environmental managers as it proliferates under drought conditions, and rapidly colonises degraded landscapes. In particular, the plant grows easily in abandonedLetter from Africa: Do Nigerians go on holiday? Published duration 7 March 2017

image copyright AFP image caption Nigerians were sceptical when President's Buhari's spokesman said he was on holiday in London

In our series of letters from African journalists, Sola Odunfa examines the attitude of Nigerians to holidaying, at a time when President Muhammadu Buhari has spent more than six weeks on "medical vacation" in the UK.

Wherever the idea of formal holidays may have come from, it was definitely not Nigeria.

A holiday is a period when people completely take time off from work and relax to relieve themselves of stress - both physical and mental.

It is meant to be a time to recharge one's batteries.

It can also be a time to indulge in travel - to see new places