272 RESPIRATION, FERMENTATION AND DIGESTION 



hand lens, and again on the second day. The beginning of 

 digestion of the albumen will be denoted by the loss of sharp- 

 ness of the edges of the egg material and that after a time the 

 outer portions are converted into a transparent fluid. 1 



347. Digestive Action of Nepenthes. Suck up a few cm. of the 

 clear liquid in the pitchers of any species of Nepenthes and place 

 in a watch glass. Immerse one or two cubes of white of an egg 

 in the albumen, cover and set in a thermostat at 35 ° C. Pre- 

 pare a second, adding a small drop of dilute hydrochloric acid to 

 the liquid. Note the appearance of the cubes a day later. The 

 digestive enzyme is variously held to be a trypsin or pepsin. 2 



348. Glands of the Pitchers of Nepenthes. Cut a cross section 

 of the glandular region of the pitchers and examine the structure 

 and character of the contents of the glands. It is to be noted 

 that the pitchers of Sarracenia have not yielded any enzyme in 

 investigations made upon them, and they are supposed to absorb 

 the products of bacterial fermentation, and simple decomposition 

 of the material finding its way into the pitchers. 3 



349. The Clotting Enzymes. The clotting enzymes repre- 

 sented in plants by rennet and pectase differ from those previ- 

 ously discussed in not being concerned with digestion, or indeed 

 to any great extent with processes in the chain of general meta- 

 bolism. Their characteristic action consists in the coagulation of . 

 substances from the solutions in which they are found, forming 

 gelatinous masses which later undergo contraction and harden- 

 ing, becoming semi-fibrous. The formation of the jelly-like ma- 

 terial may be accompanied by the separation of substances as sol- 

 uble as the original solution. Calcium has been found as an 



1 Huie, L. Action of the glands of Drosera. Quart. Jour. Roy. Mic. Soc, Vol. 39. 



2 Clautriau, G. La digestion dans les urnes de Nepenthes. Mem. Cour. e. a. 

 Mem. pub. p. l'Acad. Roy. d. Belg. 59 : 1900. 



Vines. The proteolytic enzyme of Nepenthes. Annals of Botany. 12: 545. 1898. 



n MacFarlane, J. M. Observations on pitchered insectivorous plants. Annals of 

 Botany. 7 : 403. 1893. 



Butkewitsch, W. Ueber das Vorkommen eines proteolytischen Enzyms in ge- 

 keimten Samen und seine Wirkung. Zeitschr. f. Physiol. Chemie. 32 : 1. 1901. 



