 Why is Kolin so worried about the purple berries?
Kolin found himself in a group with Jak Ammet, a third cook, and Eva Yrtok, powdered foods storekeeper. Chief Slichow emphasized that the keepers of rations could hardly, in an emergency, give even the appearance of favoring themselves in regard to food. For all Kolin could tell, he and the others were isolated in a world bounded by the rocky ridge behind them and a semi-circle of damp trees and bushes several hundred meters away. "Be a job to find anything edible here," grunted Ammet, and Kolin agreed. Yrtok paused to examine some purple berries glistening dangerously on a low shrub. Fifty meters away, Ammet sat beside the bush with the purple berries, utterly relaxed.
 They may have had adverse effects on his crewmates' mental state.
 He expected them to be a different color.  They may have had adverse effects on his crewmates' mental state.  The cook thinks that they are dangerous to eat.  If they are not edible, they will not have any food to bring back with their report.