Virtual villagers 2 - 5th Plant Puzzle?

I am having problems with the 5th puzzle on Virtual Villagers 2. I don't think any one else has this problem. I take a Master Scientist or a Trainee Doctor over to the plants to study and master them. But it always says studing plant, and then the villager just turns and shakes their head, and then sometimes it says the villager has improved with healing. I can never master the plant no matter how many times I drop them on the plant. I know where all the plants are, but I can't get them to master them.



Does anyone know how to help me? Do I need some other villager besides a Master Scientist? I am so confused and I have already passed all of the puzzles except this one and the stew one since I don't have mastered plants.



Please help..Virtual villagers 2 - 5th Plant Puzzle?
You don't need a master scientist. Any villager can understand a plant. There are six of them. 1. next to the dry grass, 2. near the thorny briars, 3. the purple daisy in the sacred area for the dead, 4. line of black flowers in the sacred area, 5. red plant near where the dam is built, and 6. lily on the southern side of the village. You should just place a villager on the plant and he or she should study it for a moment and then walk away. The bottom should say "Your villagers now understand this herb."