Classification of Plants 223 



Cane sugar by taking up a molecule of water breaks up 

 into a molecule of grape sugar (glucose) and fructose: — 



, Ci,H,,Oii + H,0 = C,H„0, + C,H,,0,, 



After this change outside the yeast cells has taken place 

 (extracellular digestion), the simple sugars are "taken into the 

 yeast cell. Here it meets with an enzyme which cannot pass 

 out of the cell. This enzyme disorganizes these sugars, where- 

 upon oxygen which was driven away from the carbon when it 

 was first formed, now recombines with it forming C0„. Not 

 all the carbon is oxydized, but the sugar is broken down into 

 carbonic acid gas and alcohol : — 



C,Hi,0, = 2C,H,0 + 2CO,. 



Fig. 196. — Spore print of a Mushroom. (Printed and photograptied by Miss 

 Etliel M. Doidge.) 



In preparation of the Kaffir beer Leting, Miss Doidge has 

 found that a mould (Mucor) effects the change from starch to 

 sugar and can also ferment some of the sugar, forming some 

 alcohol. When the Leting is fresh a bacterium causes an acid 

 fermentation of the starch of the Kaffir corn thus producing a 

 very wholesome drink which is not intoxicating. 



Many of the rusts live part of their life as parasites on one 

 host while to complete their life-history quite another host is 

 necessary. 



