PLANTS WHICH EXHIBIT MOVEMENTS IN THE CAPTURE OF PREY. 149 



seizure and digestion is one of the most curious adaptations displayed by the 

 vegetable world. 



The Venus's Fly-trap (Dioncea muscipula), represented opposite (fig. 27), in 

 half its natural size, grows wild only in a narrow strip of country in the east of 

 North America (from Long Island to Florida) in the vicinity of peat-bogs. The 

 leaves, like those of many other carnivorous plants, are grouped in rosettes round 

 the flowering axes, and for the most part rest their under surfaces either entirely 

 or partially upon the ground. Each leaf consists, first, of a flat, spatulate petiole, 

 which is, as it were, truncated in front and suddenly contracted to the midrib, and, 

 secondly, of a roundish lamina. The latter is divided by the midrib into two 

 symmetrical halves, inclined to one another at an angle of from 60° to 90° like the 

 leaves of a half-open book. Both margins of the lamina run out into from twelve 

 to twenty long, sharp teeth, which, however, do not carry either glands or any 

 other special structures on their tips. 



On the central part of each half of the leaf there are three very stiff" and sharp 

 spines, which are always shorter than the marginal teeth, and which stand up 

 obliquely. They are composed of elongated cells whose protoplasm throughout 

 life is in very active circulation. At the base of each spinous process is a short 

 cylindrical pad of tissue formed of small parenchymatous cells, and this pad allows 

 the spine to be deflected. The spines themselves are rigid and do not bend in 

 response to pressure; they are forced down on to the surface of the leaf, the pad of 

 tissue referred to acting as a hinge. In addition to these processes, glands are 

 scattered over the whole upper surface of the lamina. They look like the 

 shortly -stalked glands of a butter wort leaf, are composed of some twenty -eight 

 small cells, are purple in colour, and capable of secreting a mucilaginous liquid. 

 Little trichomes, stellate hairs, are also borne on the edge of the leaf between the 

 sharp teeth, and also on the under-surface. 



No visible change is produced by a blow or shock or by pressure affecting the 

 whole plant or leaf, as might be caused by wind or falling drops of rain, nor even 

 by injuries to the petiole or back of the lamina. But as soon as the upper surface 

 of the lamina is touched, the two lobes, hitherto at right angles, approach one 

 another until the sharp marginal teeth are interlocked, and the body touching the 

 leaf is inclosed within two walls (fig. 28 ^). When the places beset with purple 

 glands are alone excited by contact with the object, this inflection and closing 

 follows very slowly; but if one of the six spines projecting in trios from the two 

 foliar lobes is ever so lightly touched, the leaf shuts up within 10-30 seconds, i.e. 

 quickly and steadily; an action best compared to the closing of a half -open book. 

 The teeth standing at the edge of the leaf lock into one another on these occasions 

 like the fingers of clasped hands. The lobes, however, whose surfaces were hitherto 

 plane, become at the moment of closing somewhat concave, so that when contracted 

 they do not lie flat against one another but inclose a cavity, the contour of which 

 nearly corresponds with that of a bean. 



The further changes and processes now ensuing depend upon whether the 



