cacti, cactuses, or cactus

On the first part of the journey
I was looking at all the life
There were plants and birds and rocks and things
There was sand and hills and rings
The first thing I met was a fly with a buzz
And the sky with no clouds
The heat was hot and the ground was dry
But the air was full of sound


No known fossils of cacti exist to throw light on their evolutionary history. The geographical distribution of cacti offers some evidence, cacti are plants of South America and mainly southern regions of North America. This suggests the family must have evolved after the ancient continent of Gondwana split into South America and Africa, which occurred during the Early Cretaceous, around 145 to 101 million years ago.