Action of Glands. 525 



The Drosera rotundifolia, or round-leafed Sundew, is native both in 

 this country and Europe. It is a remarkable plant, and has been ex- 

 haustively described by Darwin. (Insectivorous Plants.) The leaves 

 of this plant are circular, a little over half an inch in diameter, and 

 they are covered with glands which are set upon stalks or pedicels, a 



gland with its stalk being denominated a 

 tentacle. The average number of these 

 tentacles is nearly 200 per leaf. The ten- 

 tacles in the central part of the leaf are 

 short, and stand upright. They increase 

 in length going outwards, and incline more 

 and more outwardly until the margin of 

 the leaf is reached, where they recline hor- 

 izontally, and are sometimes nearly ^ of an 

 inch in length. The stalks of these tenta- 

 cles are flexible, and contractile, particu- 

 larly near their base, and under stimula- 

 tion they bend over toward the center of 

 the leaf, each carrying the gland on its 



FIG. 249.-Drosera Rotundifo- summit with it. This gland is less than 

 lia (round-leaved). Part of t\\n ten- t f u : Hinrnpfpr nnrl tn it nrl 



tacles curved over and holding T^o OI an mcn m aiameter > ana 



if meat. (Darwin.) heres the drops of vigdd secret ion which it 



distills, and the glisten of which in the sunlight suggests the name, 

 sundew. When the tentacles in the central part of the leaf are agi- 

 tated by being pressed and shaken, as by the struggling of an insect in 

 the sticky secretion, a stimulation is conveyed to the tentacles on the 

 margin of the leaf. * ' The nearer ones are first affected, and slowly 

 bend toward the center, and then those farther off, until at last all be- 

 come closely inflected over the object. This takes place in from one 

 hour to four or five or more hours." The stimulation which travels 



from the tentacles which are agitated 

 by the foreign substance, arouses both 

 motor action in the stems of the mar- 

 ginal tentacles fry which they are 



bent, and glandular action in causing 

 FIG. 250. Eight different forms taken 



by the protoplasm in a cell of a tentacle the glands to secrete their fluid. This 

 of Drosera Rotundifolia, during a period 



of 15 minutes. (Darwin.} fluid contains a ferment, and is a pep- 



tic agent, and, as Darwin discovered, it also has an antiseptic quality, 

 and prevents animal matter in contact with it becoming putrid. The 

 tentacles remain clasped over nitrogenous matter much longer than over 

 other substances, sometimes not re-opening again for seven days. But 

 if they are stimulated to close by an agitation which affords nothing 

 they can digest, they open again within 24 hours. The activity of the 

 protoplasm in the tissues of Drosera, is shown by fig. 250. 



