Anatomy and Physiology. 91 



cup when no stream is at hand to satisfy their thirst. The blad- 

 der tillandsia will hold nearly a quart of rain water. The tra- 

 veller, Dam pier, speaking of this plant, says, " We stuck our 

 knives into the leaves, just above the root, and that lets out the 

 water which we catch in our hats, as I have done many times 

 to my great relief." The side-saddle plant will scarcely hold 

 above a gill, and unless when pierced by some insect, is gene- 

 rally full. The two latter species we have mentioned, collect 

 the water and do not secrete it themselves. 



In our estimation, the most wonderful change the petiole or 

 leaf itself undergoes is that of the fly-trap. Nuttall says that it 

 has hitherto been solely found in the immediate vicinity of Wil- 

 mington, in North Carolina, where it occurs in abundance in 

 mossy bogs. The leaf is thick, opaque, and wedge-shaped, and 

 jointed to its extremity is the curious and celebrated trap. This 

 is of a circular form, and completely edged with peculiar bristles 

 which fit into each other perfectly when the leaf is closed. The 

 irritability resides chiefly in certain glandular or secreting hairs, 

 which are disposed on either side the trap lobes. Should a fly 

 or any other insect alight on the trap, it instantaneously folds up 

 and causes a sure and speedy death. Some have supposed that 

 they did this to provide themselves with nutriment, by feeding 

 on the elements which putrefaction set free. It may be so ; but 

 from their situation we would conjecture they were already plen- 

 tifully supplied with such aliment. The sensitive plant will fold 

 itself up to escape the touch, but there are some that, to show 

 signs of sensibility, need neither sun-light nor touch. The mov- 

 ing plant is, as Linnaeus observes, wonderful on account of its 

 voluntary motion. No sooner, continues he, had the plants raised 

 from the seed acquired their ternate leaves, than they began to 

 be in motion this way and that. This movement did not cease 

 during the whole course of their vegetation, nor were they ob- 

 servant of any time, order or direction ; one leaflet frequently 

 revolved, whilst the other on the same petiole was quiescent ; 

 the whole plant was very seldom agitated, and that only during 

 the first year; but sometimes most of the leaves would be in 

 motion at the same time. This motion does not depend on any 

 accidental or external cause, such as touching, heat, cold, light 

 or darkness, for they will neither excite it nor prevent its continu- 

 ance. Bractea or floral leaves are peculiar to some plants ; they 



