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manner that tlio upper surfaces of their leaves avoid facing the 

 zenith at night, others, as the oxalis or wood sorrel, bring their 

 surface faces in contact, thus protecting the upper part from chill 

 by radiation. It has long been known that the leaflets of the 

 genus Averrhoa sleep at night and move spontaneously at daylight, 

 also that they are sensitive to touch. Lupmus pilosus has similar 

 habits. 



Some of the plants before mentioned have been noted as 

 sensitive plants, but those generally so termed deserve our further 

 examination. Amongst the best known of these is the fly trap 

 (Diotiea fucifera). In this plant the upper leaves are armed with 

 bristly points or hairs which surround their margins, and from the 

 mid-rib the two sides of each leaf close together quickly upon 

 being touched, which enables them to imprison a fly or other insect 

 that may alight upon the surface. In Mimosa pudica a slight 

 touch at the extremity of one leaflet causes the depression of that 

 leaflet, this movement is communicated to its neighbour and so on 

 in succession ; after an interval the plant regains its equilibrium 

 and the original position of the leaf is resumed. Sensitive plants 

 like animals get exhausted when the stimulus is applied too often, 

 and require rest to recover their powers. 



As possessing most remarkable motive action, as well as being 

 influenced by certain stimulants, and capable of transmitting this 

 influence to other parts of the plant. Drosera, in interest, stands at 

 the head of all sensitive plants. I shall not enter now on those 

 other properties it possesses in common with many animals, but 

 confine my remarks to its motile peculiarities. 



The commonest and therefore best known of the genus 

 (^Drosera rotundifolia) grows on bogs, and its leaves are armed with 

 pin-headed glands. These glandular filaments (we might call them 

 tentacles) are from 150 to 200 in number, each surrounded by an 

 extremely viscid secretion, which glistening in the sun has given 

 rise to the plant's poetical name Sundew. The tentacles on the 

 central part of the leaf are short and stand upright, towards the 

 margin they become longer, and more inclined outwards ; each 

 consists of a thin straight hair-like pedicel, carrying a flattened 

 gland upon its summit, whilst spiral vessels accompanied by simple 

 vascular tissue branch off from the vascular bundles in the blade of 

 the leaf, and run up all the tentacles into the glands. 



Such is the structure of the leaf, and if a small organic or 

 inorganic object be placed on it, the touched glands transmit a motor 

 impulse to the marginal tentacles; the nearer ones are first affected, 

 and slowly bend towards the centre, and then those further off, until 

 at last all become closely inflected over the object. This occupies 



