SEEDS AND SEEDLINGS 71 



previously prepared. Heat the mixture, which should now have 

 a blue color, in the test tube. If grape sugar is present in consid- 

 erable quantity, the contents of the tube will turn first a greenish, 

 then }-ellow, and finally a briclc-red color. Smaller amounts will 

 show less decided red. No other substance than sugar will give 

 this reaction. If Benedict's test^ is used, a colored precipitate 

 will appear in the tost tube after boiling. 



Starch changed to Grape Sugar in the Corn. — That starch is 

 being changed to grape sugar in the germinating corn grain can 

 easily be shown if we cut lengthwise through the embryos of half 

 a dozen gi-ains of corn that have just begun to germinate, place 

 them in a tost tube with some Fehling's solution, and boat almost 

 to the boiling point. The3^ will be found to give a reaction show- 

 ing the presence of sugar along the edge of the cotyledon and 

 between it and the endosperm. 



Digestion. — This change of starch to grape sugar in the corn 

 is a process of digestion. If you chew a bit of unsweetened cracker 



' Benedict's Test fob Grape Suqab 



This test, known from its author as " Bcnodict's test," will be found described 

 in the 11*09 edition of Hawk's Bwclumical Chemistry. In the latter it ia the one 

 labeled "Second Solution." 



PREPARATION 



Copper sulphate . . . 17.3 grama 



Sodium eitrate 173. grams 



Sodium carbonate (anhydrous) 100. grams 

 Make up to 1 liter with distilled water 



With the aid of heat dissolve the sodium citrate and carbonate in about 600 o.c. 

 of water Pour through folded filter paper into a glass graduate and make up to 

 ,s.j0 r.c. with di.-tilled water. 



Dissolve the copper sulphate in about 100 e.c. of water and make up to 150 c.c. 

 with distilled water. 



Pour the carbonate-citrate solution into a large beaker or casserole and add 

 the copper sulphate solution slowl,\- with constant stirring. 



The mixed solution is read\- for use and ilnes mil ddcriorntr on xlandina. 



For use add to ', c.c. of the solution in a test tube S drops (more does not ilisturb 

 the experiment, but S drops is sufficient for a t;ociil result) of the solution \mder 

 examination. Boil for one or two minutes and let cool. If iirape sugar be piesenl. 

 the entire body of the liquid will he filled with ,i precipitate which may be red, 

 yellow, or green in color, depending upon the amount of suiiar present. Kicht 

 drops of 1 per cent dextrose will >'icld precipitates of larne amounts. 



The posiliic reaction w the pnripilnlr. not the color. On this a lunt the test 



may be applied as well in artificial light as in daylight. 



