The really interesting point is connected with these central jointed or trigger hairs; they are extremely sensitive. But when they are touched it is not they themselves that are affected, but the entire circular end of the leaf! Suppose an insect wanders on to the leaf and reaches one of these semicircular halves, nothing happens until it touches one of these hairs, but then _both_ halves suddenly close together, exactly like an ordinary rat-trap! The teeth on the edges of the halves interlock like the teeth of a trap, and the insect is caught and imprisoned. Its body is slowly digested away and goes to nourish the plant. The use of the joint in the sensitive hairs can be easily perceived, for when the two halves shut up together, the hairs fold down exactly like the funnel of a river steamboat when it passes under a bridge. The closing of the two halves, which has been well compared to shutting up a half-open book, is very quick, as it does not take more than ten to thirty seconds. There is an abundant flow of "gastric juice," but the leaf takes a long time to digest its food. It may require three weeks to finish one insect. Moreover, if overfed, it may turn a bilious or dyspeptic yellow colour, and wither or even die. It only shuts for a short time if a grain of sand touches the sensitive hair, and, like Drosera, is not deceived in its food. The Dionæa, Drosera, the Sensitive Plant, Mimulus, Barberry, and others, all show us clearly that plants somehow or other act as if they were conscious of what they ought to do. In fact, in all these cases, it is scarcely possible to help believing in some sort of rudimentary nervous system. At any rate Wordsworth comes near this belief, for he has written:-- "It is my faith, that every flower that blows Enjoys the air it breathes." CHAPTER XXVIII MOSSES AND MOORS Peat-mosses and their birds--Moorlands--Cotton-grass--Scotch whisky--Growth of peat-moss--A vegetable pump--Low-lying and moorland mosses--Eruptions and floods of peat--Colonizing by heather and Scotch fir--Peat-mosses as museums--Remains of children and troopers--Irish elk--Story of the plants in Denmark--Rhododendrons and peat--Uses of peat--Reclaiming the mosses near Glasgow. In Great Britain in this present year one finds exceedingly few places where the influence of man cannot be traced. Over most of the country, indeed, it is impossible to discover a single acre of land where Nature has been allowed to go on working at her own sweet will without interference or restraint. But near Stirling, between the Lake of Monteith and the sea, there is a wide, desolate valley which is probably in exactly the same condition as it was when the Roman legions halted to reconnoitre before Agricola passed onwards to Perth and Aberdeen.