1 68 PLANT LIFE. 



chlorophyll bodies, hut is prohahly a transformation product 

 from a sugar, to which it is closely akin chenn'cally. 



234. 2. Proteids. — The formation of [iroteids is e\'en 

 more obscure. Apparently at some point in the series of 

 changes following the formation of formaldehyde, molecules 

 of nitrogen are added to form an amid. Amids, especially 

 asparagin, leucin, and tyrosin, are common in plants. They 

 may also be p.roduced by the use of carbon, hydrogen, and 

 oxygen from complex carbohydrates by katabolism (• 33S). 

 They are soluble in water, crystallizablc, and, hence, can be 

 carried bv osmosis from cell tcj cell. From these, by the 

 addition of sulfur and phos]ihorus, proteids are formed, but 

 neither the steps in the process nor its conditions are well 

 understood. Apparently the formation of amids occurs in 

 green tissues and nnder the inlluence of light. It is probable 

 that even among tlie green plants the formation of proteids 

 takes place in other parts tlian the green tissues, as it is 

 certain that this occurs also among the colorless plants. The 

 jiroteids whi( h are built up I'rom tlie amids arc used directly 

 in the repair of i)rotoplasm. Since < ar])o]iydrates are neces- 

 sary to the formation ol piroteids, and sin<;e they can be 

 manufactured only by tire green plants under the inlluence of 

 light, it will be seen how essential these p)lants are for the 

 world's food supply. 



E. Storage and translocation of food. 



235. Storage and transfer. — lioih in thi.' colorless and 

 green plants it is necessar)- that the foods made or absorbed 

 should be transferred from one yo\x\\. to another wliere they 

 are to be used. The larger the plant, the more imp>ortant 

 does this transfer become. In many plants, also, it is 

 desirable that a supply of reser\'e food be storeil for use when 

 a supjily is no longer a\'ailable from the outside or by 

 manufactiu'c. 



