522 Dynamic Theory. 



because they grow in clusters of four. Four arms take root at the same 

 place, from a short pedicel, and radiate their extremities in four direc- 

 tions. Just inside the mouth the processes have two arms instead of 

 four, and they are called bifid processes. Darwin ascertained that these 

 arms have the power of absorbing some of 'the matters held in solution 

 in the water inside of the bladder. The little animals getting in there, 

 die and decay, and are dissolved in the water, and thus furnish subsist- 

 ence to the plant. 



The Butterwort ( Pinguicula vulgaris ), which belongs to the Bladder- 

 WOrt family, is found in Northern U. S. and Europe, and is another in- 



FIG. 245. Two leaves of Pinguicula or Butter- 

 wort. 



a. Eight edge of leaf closing over bits of meat. 

 6. Left edge closing over flies placed upon it. 



sect-catching plant. A grown leaf of 

 this plant is about 1 inches long and f 

 inch wide. About eight leaves radiat- 

 ing from a common center, some lying 

 flat on the ground and others above them 

 and standing nearly upright, form, on 

 the whole, a sort of rosette. The mar- 

 gins of the leaves are curved inwards. 

 The upper surfaces of the leaves, ex- 

 cept the edges, are covered with glands 

 supported upon pedicels. The glands 

 secrete a viscid, colorless fluid, which is so sticky as to hold insects 

 which happen to get on the leaf. This secretion becomes more copious 

 and is acid when insects are caught. The secretion, when acid, ' ' has 

 the power of quickly dissolving, that is, of digesting the muscles of in- 

 sects, meat, cartilage, albumin, fibrin, gelatine and casein, as it exists in 

 the curds of milk." This secretion is, however, not able to dissolve 

 starch. The secretion which was caused by depositing a piece of starch 

 on the leaf, did not become acid. The presence of nitrogenous matters 

 upon the glands, while causing them to secrete, also causes the margins 

 of the leaves to infold toward the midrib, so as to inclose the object. 

 If the object is near the end of the leaf, the edges opposite to it are in- 

 curved, while the edges further down the leaf are not affected. 



The Droseracese, or Sun Dew Family, comprise six genera, all of which 

 capture insects and digest and appropriate them. Three genera of them, 

 viz. , Drosophyttum, Roridula and ByUis, detain the insects solely by 

 means of a sticky substance which they secrete from the glands upon 

 their leaves. One genus, the Drosera, also has the viscid secretion upon 

 which the insects stick, but the leaves are, in addition to this, provided 

 with flexible filaments or tentacles, which, when an insect is caught, 



FIG. 245. 



