What is interesting about this line from "The Interlopers" is that Georg's situation of being blinded by the blood trickling across his eyes is symbolic of his mental attitude right before the tree branch breaks as he has been blinded in his hatred and has desired to shed the blood of his enemy, Ulrich von Gradwitz, this very night of their encounter.
In fact, it is also symbolic of his enemy's feelings, as well, since right before lightning hit the huge beech tree,
The two enemies stood glaring at one another for a long silent moment. Each had a rifle in his hand, each had hate in his heart and murder uppermost in his mind.
But, in ironic twists to Saki's story, this shedding of blood from a source of Nature, rather than from the heart and hands of man, brings about the amelioration of the old enemies as they speak of how they will extend courtesies to each other. However, just as they are unable to wipe away their blood, the two former enemies are also unable to undo their vulnerable situation and they meet a terrible fate as, in ironically, the two hunters become the hunted.