You do not see it, but they are at work all the time.

They are insects--I say it without intending to speak ill of them, indeed in this case their action may even be praiseworthy! They are insects, which, when they wish to kill a plant, do not touch the fruit, the flowers, the leaves, or the roots I may even say, for there a poisonous draught might reach them, or a spade reveal their presence, and they do not wish to be reached, do not wish to be seen.

They bore into the marrow.

These two have already reached the marrow.

Perhaps it may not be for a month, perhaps not for two months; but the plant is doomed to wither, and wither it must!" "But what do you yourself think about it ?" Maria inquired.