V] HYDROLYZING ENZYMES 05 



The extraction of poctinogen, etc. in the above experiments can equally well be 

 carried out with other material, e.g. ripe gooseberries, ra!Si)berries and .strawbei'ries, 

 using exactly the same methods. 



Expt. 69. Preparation of pectinogen from Turnips. Take two full-sized turnips 

 and mince them finely in a mincing machine. Then wrap the mass in a piece of 

 strong unbleached calico and press out the juice as completely as possible in a press. 

 The juice contains little pectinogen and can be thrown away. The pressed mass is 

 then thrown into 0-5 ^'/o ammonium oxalate solution heated to 80-90° C. on a watei-- 

 bath and stirred to make a paste. The liquid is again rapidly pressed out in the press. 

 To the viscid extract an equal volume of 96 "/o alcohol is added, and the pectinogen 

 separates out as a voluminous gelatinous precipitate. This is filtered off and, when 

 pressed free from alcohol and dried, can be used for tests as in the previous experi- 

 ments. 



The gelatinizatiun of pectinogen can also be brought about by certain 

 enzymes termed pectases which are found in the juices of various plants, 

 i.e. root of Carrot (Daucus Carota) and leaves of Lucerne (Medicago 

 sativa), Lilac {Syringa vulgaris) and Clover {Trifoliam pyxitense). 



Expt. 70. Action of pectase on pectinogen. Make an extract of either Lucerne or 

 Clover leaves by pounding them in a mortar with a little water, and then filter. Add 

 the filtrate to some of the pectinogen solution prepared in Expt. 66 or 69. On 

 standing a gelatinous precipitate will be produced. Should the reaction be slow, it 

 may be accelerated by placing the mixture in an incubator. 



Celluloses. 



Celluloses are very important polysaccharides. They form constituents 

 of the structural part of all the higher plants. The cell-wall of the 

 young cell consists entirely of cellulose, but in older cells the walls may 

 be lignified, cuticularized, etc., i.e. the cellulose may be accompanied by 

 other substances such as lignin, cutin, mucilage, etc. In the light of 

 these facts the term cellulose is made to include : 



1. Normal celluloses. 



2. Compound celluloses. 



(rt) Ligno-celluloses. 

 {h) Pecto-celluloses. 

 (c) Adipo- or cuto-celluloses. 



3. Pseudo- or Reserve celluloses. 



True or normal cellulose. Of this substance, as we have said, 

 many cell-walls are composed. The most familiar form of cellulose is 

 cotton, which consists of haii's, each being a very long empty cell, from 

 the testa or coat of the seed of the Cotton plant {Gossypium herbaceion). 



