It's our third week in the Guyanese rainforest, and we've hiked out to the base of a small but fast-moving waterfall to see what plants we can collect around the wet rock face. Getting to it involves scrambling over a series of large boulders with long drops to one side. It would be a nerve-wracking climb at the best of times, but as we get about a third of the way up, it starts to pour in that abrupt fashion particular to the tropics. The mossy rocks instantly become slippery to the touch, and it isn't clear whether it's less dangerous to keep going or try descending back the way we've come.

We decide to keep going, and manage to get to the rock face to make some collections, including a few delicate orchids clinging to the stone. But it's obvious we aren't going to get back down the way we've come. One of the field assistants who has stayed below circles around and cuts a path through the dense forest near the top of the falls. It's an alternate way out, but we still have to get up to the head of the trail he's cut. That means climbing a near-vertical wall of wet cut-grass, a plant named for its hand-slicing capacity. I press myself into it, grab the cut-grass and try to scramble up. Anytime I stop scrambling for a moment, I start to backslide, slipping down the grassy wall toward the huge boulders and rushing water below.

Waterfalls curve around a bend near the top of a tepui | (Courtesy of the author/Courtesy Narratively)

After a few minutes of frenzied activity, I peek my head over the top of the wall. As someone with a profound snake phobia, I'm considering that the ill-timed appearance of one right now would be the end of me. The universe must have laughed at that thought, because just then, what looks like a terrier-sized rat pokes its face out of the bushes inches in front of me. I'm so startled that I nearly lose my grip and plummet to a grisly fate below.

Some deeply buried instinct for survival thankfully surfaces just in time and I grab the grass before the point of no return. It takes the entirety of my willpower to remain motionless in front of what turns out to be a creature the Guyanese call a labba: Cuniculus paca, a harmless South American rodent that can reach up to 25 pounds. Making our way back to our field site, feeling the exhaustion that follows in the wake of a flood of adrenaline, it occurs to me that I've just risked life and limb for the sake of some dried plants.

It's May 2009. We're a team of two American botanists, a local flora expert, two field assistants, a local guide and observer from the Amerindian community on whose land we are collecting specimens, and me, a Canadian PhD. student in plant systematics. We're here in Guyana to conduct a "general sampling" of the flora of an understudied region of the Guiana Shield, a billion-year-old, Precambrian geological formation along the northeastern edge of South America. This means that we'll be collecting anything and everything, from tiny clumps of moss right up to samples from the tallest trees of the canopy. It's difficult and hazardous work, but this expedition will bring in more than 700 collections belonging to 90 different plant families, some species of which may be new to science.

The expedition leader and I are legume specialists, so we'll be keeping a particular eye out for plants in that family. Depending on the abundance of a given plant, we'll take anywhere from one to 10 collections of it. Each sample will be pressed and attached to a heavy sheet of paper labeled with descriptions of what it is and where it came from. In any case where only a single collection of a plant can be made, it will always go to the University of Guyana, because this is their flora. Any additional samples will be distributed to the foremost herbaria (plant specimen collections) of the world: the Smithsonian, London's Kew Gardens, New York, Paris, the Netherlands, and elsewhere. Researchers all over the world will use them to investigate scientific questions about the plants and ecosystems that exist here — and how they may be changing.

Looking down the Kako River, a tabletop mountain, or tepui, is seen in the background. | (Courtesy of the author/Courtesy Narratively)

We are traveling by boat up the Mazaruni and Kako rivers, east of the Venezuelan border in the Pakaraima Mountains. We set up camp for a few days and make day hikes, moving slowly over the terrain, collecting whatever we find, unless the plant is potentially rare or threatened, and then it is left alone — better it remain unknown but alive.

Each day we hike a new area with different terrain: mountainside, swamp, riverbank, a patch of savannah. Here in Guyana, the mountains are of a flat-topped variety called tepuis, or tabletop mountains, unique to this part of the world. They jut abruptly up through the jungle in isolation, rather than as a continuous range, like a series of ancient tree stumps grown over with moss — making each one home to a group of unique indigenous plant species.

At the moment, we are days from what I would recognize as a hospital, and the heat and humidity of the tropics make infection and exhaustion real threats, narrowing the margin of error should something go wrong. A lifetime of being close to help and having access to modern medicine has made me dangerously complacent about the types of risks that come with isolation, and I'm in my 20s, so I think I'm immortal anyway.

Today, we're collecting near a swamp. The other two botanists and the two field assistants, Delph and Timo, have set out into the swamp to see what interesting specimens may be found there. Knowing how common water snakes are in this region, my phobia and I have opted to stay by the edge of the water and catalog what I can find there. I collect for a time, but my teammates are gone for what ends up being hours.

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