I still have the copy of Fossils, A Guide to Prehistoric Life –A Little Guide in Colour that as a child I often read before lights out. Though its spine is now broken and its pages battered, the picture on page 46 – Raymond Perlman's impression of an Upper Carboniferous (310–280 million years ago) swamp – retains all its mystery. A dragonfly with wings 30 inches across darts among the fantastic trees snatched from someone's dream; an amphibian on a fallen log lies still, perhaps waiting to become the first reptile. Tranquility abounds. And yet, amid all the unfamiliarity of this earlier world, Perlman painted plants so recognizable I immediately knew what they were, and that they – or at least some close relative – still grew by the river near my home: horsetails. Horsetails were, in fact, already ancient by the time of the Upper Carboniferous. Perlman knew this and painted them prominently in an earlier scene of the Devonian (which began 405 million years ago), depicting them with the same simple structure they have today: a stem plus whorls of needle-like leaves. He could not, however, take the opportunity to show what horsetails could really do, for over the Carboniferous (345–280 million years ago) they were reaching for the sky, often towering over 40 feet in height. Mary Parrish, a scientific illustrator with the Smithsonian National Museum of Natural History, included some large specimens in her more recent (and beautiful) reconstruction of a late Carboniferous wetland (www.mnh.si.edu/ete/ETE_Research_Reconstructions_Carboniferous.html), but for a down-to-Earth impression of how an ancient forest of Calamites (an extinct genus of branched horsetails) may have looked, Walter Myers' rendition (http://fineartamerica.com/featured/a-forest-of-calamites-and-asteroxy-lon-walter-myers.html) would be hard to beat. Equisetum myriochaetum at the Royal Botanic Garden, Edinburgh, Scotland. But the most remarkable plant in the forest of Canelos is a gigantic Equisetum [a modern horsetail] 20 feet high, and the stem nearly as thick as the wrist! It extends for a distance of a mile on a plain bordering the Pastasa, but elevated some 200 feet above it, where at every few steps one sinks over the knees in black, white, and red mud. A wood of young larches may give you an idea of its appearance. I have never seen anything [that] so much astonished me. I could almost fancy myself in some primeval forest of Calamites, and if some gigantic Saurian had suddenly appeared, crushing its way among the succulent stems, my surprise could hardly have been increased. Could something of prehistory's botanical behemoths still exist? I could not rush to the Pastasa (or Pastaza) River in Ecuador to see for myself, but a little research showed that the country is indeed home to giant horsetails, including Equisetum myriochaetum, a species that grows across parts of northern South America, Central America, and southern Mexico. Commonly known as the Mexican giant horsetail, it is said to regularly reach 15 feet in height, with one specimen measuring 24 feet. What's more, I would have no need to travel halfway around the world to see one, for I discovered that the Royal Botanic Garden in Edinburgh, Scotland, had the species in its list of accessions, and in a few weeks I would be traveling to that city where my son was to start university. I found my giants on a Sunday morning, nestled in the northwest corner of the Garden's fern house. There they were, 400 million years since their kind first appeared, 10 feet tall and striving toward the light, proud and straight, majestic in their enduring simplicity. Standing before them, surrounded by fern trees, liverworts, and moist soil, I no longer had any need for an artist's impression of a Carboniferous landscape – I was in one. True, the horse-tails were smaller than their mighty ancestors of old, but there was no mistaking the scene. As I stood there, I remembered Spruce's words and Perlman's drawing that had inspired me all those years ago. If a dragonfly with a 30-inch wingspan had suddenly appeared, darting between the succulent stems, my surprise could hardly have been increased.