This power of reopening quickly after the filaments have been accidentally touched by blades of grass, or by objects blown on the leaf by the wind, as occasionally happens in its native place,* must be of some importance to the plant; for as long as a leaf remains closed, it cannot of course capture an insect. When the filaments are irritated and a leaf is made to shut over an insect, a bit of meat, albumen, gelatine, casein, and, no doubt, any other substance containing soluble nitrogenous matter, the lobes, instead of remaining concave, thus including a concavity, slowly press closely together throughout their whole breadth. As this takes place, the margins gradually become a little everted, so that the spikes, which at first intercrossed, at last project in two parallel rows. The lobes press against each other with such force that I have seen a cube of albumen much flattened, with distinct impressions of the little prominent glands; but this latter circumstance may have been partly caused by the corroding action of the secretion. So firmly do they become pressed together that, if any large insect or other object has been caught, a corresponding projection on the outside of the leaf is distinctly visible. When the two lobes are thus completely shut, they * According to Dr. Curtis, in ‘Boston Journal of Nat. Hist,’ vol. i 1837, p. 123. [page 308] resist being opened, as by a thin wedge driven between them, with astonishing force, and are generally ruptured rather than yield. If not ruptured, they close again, as Dr. Canby informs me in a letter, “with quite a loud flap.” But if the end of a leaf is held firmly between the thumb and finger, or by a clip, so that the lobes cannot begin to close, they exert, whilst in this position, very little force.