‘Quite a specimen, isn’t it,’ Cahuella said.
‘The most recent fusion probably only happened a few weeks ago,’ Dieterling said, as comfortable with the ghoul as his master. ‘Take a look at the cell-type gradient here.’
The doctor ambled forward to see what Dieterling was talking about.
Dieterling had unpacked a slim grey device from the waist pocket of his hunting jacket. Of Ultra manufacture, it was the size of an unopened Bible, set with a screen and a few cryptically marked controls. Dieterling pressed one side of the device to the helix and thumbed one of the buttons. In shades of pale blue, vastly magnified cells appeared on the screen. They were hazy cylindrical shapes, packed together haphazardly like body bags in a morgue.
‘These are essentially epithelial cells,’ Dieterling said, sketching a finger across the image. ‘Note the soft, lipid structure of the cell membrane — very characteristic.’
‘Of what?’ Gitta said.
‘Of an animal. If I took a sample of your liver lining, it wouldn’t look too dissimilar to this.’
He moved the device to another part of the helix, a little closer to the trunk. ‘Now look. Totally different cells — arranged much more regularly, with geometric boundaries locked together for structural rigidity. See how the cell membrane is surrounded by an additional layer? That’s basically cellulose.’ He touched another control and the cells became glassy, filled with phantom shapes. ‘See those podlike organelles? Nascent chloroplasts. And those labyrinthine structures are part of the endoplasmic reticulum. All these things are defining characteristics of plant cells.’
Gitta tapped the bark where Dieterling had made the first scan. ‘So the tree is more like an animal here, and more like a plant — here?’
‘It’s a morphological gradient, of course. The cells in the trunk are pure plant cells — a cylinder of xylem around a core of old growth. When the snake first attaches itself to the tree, wrapping around it, it’s still an animal. But where the snake comes into contact with the tree, its own cells begin to change. We don’t know what makes that happen — whether the triggering cue comes from something in the snake’s own lymphatic system, or whether the tree itself supplies the chemical signal to begin fusion.’ Dieterling indicated where the helix merged seamlessly with the trunk. ‘This process of cellular unification would have taken a few days. When it was over, the snake was inseparably attached to the tree — had, in fact, become part of the tree itself. But most of the snake was still an animal at that point.’
‘What happens to its brain?’ Gitta asked.
‘It doesn’t need one anymore. Doesn’t even need anything we’d exactly recognise as a nervous system, to be frank.’
‘You haven’t answered my question.’
Dieterling smiled at her. ‘The mother’s brain is the first thing that the juveniles eat.’
‘They eat their mother?’ Gitta said, horrified.
The snakes merged with their host trees, becoming plants themselves. It only happened when the snakes were in their near-adult phase, large enough to spiral around the tree all the way from the ground to the canopy. By then young hamadryads were already developing in what passed for the creature’s womb.
The host tree had almost certainly already seen several fusions. Perhaps the original, true tree had long since rotted away, and what remained were only the locked spirals of dead hamadryads. It was likely, however, that the last snake to attach itself to the tree was still technically alive, having spread its photosynthetic cowl wide from the top of the tree, drinking sunlight. No one knew how long the snakes could have lived in that final brainless plant-phase. What was known was that another near-adult would arrive sooner or later and claim the tree for itself. It would slither up the tree and force its head through the cowl of its predecessor, then spread its own cowl over the old. Deprived of sunlight, the shadowed cowl would wither away quickly. The newcomer would fuse with the tree, becoming mostly plant. What little animal tissue remaining was there only to supply the young with food, born within a few months of the fusion. Some chemical trigger would cause them to eat their way out of the womb, digesting their mother as they went. Once they had eaten her brain, they would chew their way down the spiral length of her body, until they emerged at ground-level as fully formed, rapacious juvenile hamadryads.
‘You think it’s vile,’ Cahuella said, reading Gitta’s thoughts expertly. ‘But there are life-cycles amongst terrestrial animals which are just as unpleasant, if not more so. The Australian social spider turns to mush as her spiderlings mature. You have to admit it has a kind of Darwinian purity to it. Evolution doesn’t greatly care about what happens to creatures once they’ve passed on their genetic heritage. Normally adult animals have to stick around long enough to raise their young and safeguard them from predators, but hamadryads aren’t constrained by those factors. Even juveniles are nastier than any other indigenous animals, which means there’s nothing to protect them against. And they don’t need to learn anything they don’t already have hardwired into them. There’s almost no selection pressure to prevent the adults from dying the instant they’ve given birth. It makes perfect sense for the juveniles to gorge themselves on their mothers.’
It was my turn to smile. ‘You almost sound like you admire it.’
‘I do. The purity of it — who couldn’t admire that?’
I am not sure quite what happened then. I was looking at Cahuella, with half an eye on Gitta, when Vicuna did something. But the first flash of movement seemed to have come not from Vicuna but from my own man Rodriguez.
Vicuna had reached into his jacket and pulled out a gun.
‘Rodriguez,’ he said. ‘Step away from the tree.’
I had no idea what was happening, but I saw now that Rodriguez’s own hand was buried in his pocket, as if he had been on the point of reaching for something. Vicuna waggled the end of his gun emphatically.
‘I said step away.’
‘Doctor,’ I said, ‘would you mind explaining why you are threatening one of my men?’
‘Gladly, Mirabel. After I’ve dealt with him.’
Rodriguez looked at me, eyes wide in what looked like confusion. ‘Tanner, I don’t know what he’s on about. I was just going for my rations pack…’
I looked at Rodriguez, then at the ghoul.
‘Well, doctor?’
‘He has no rations pack in that pocket. He was reaching for a weapon.’
It made no sense. Rodriguez was already armed — he had a hunting rifle slung over one shoulder, just like Cahuella.
The two of them faced each other, frozen.
I needed to make a decision. I nodded at Cahuella. ‘Let me handle this. Get yourself and Gitta away from here; away from any possible line of fire. I’ll meet you back at the camp.’
‘Yes!’ Vicuna hissed. ‘Get away from here, before Rodriguez kills you.’
Cahuella took his wife and stepped hesitantly away from the tableau. ‘Are you serious, doctor?’
‘He seems adequately serious to me,’ Dieterling murmured. He was already edging away himself.
‘Well?’ I said, towards the ghoul.
Vicuna’s hand was trembling. He was no gunman — but no kind of marksmanship would have been necessary to take out Rodriguez at the distance that spaced them. He spoke slowly and with forced calm. ‘Rodriguez is an impostor, Tanner. I received a message from the Reptile House while you were here.’