Few explorations have been so fruitful as this six years' journey.
All experiments are fruitful if you don't have any preconceived notions about the results.
Experience with epidemics, dearly bought in the past, has shown that one fruitful cause is the laying open to the inroads of some Fungus or insect, hitherto leading a quiet endemic life in the fields and forests, large tracts of its special food, along which it may range rampant without check to its dispersal, nutrition and reproduction.
"Good. That will make this a fruitful conversation," the Watcher said.