MINERAL SUBSTANCES REQUIRED BY PLANTS 33 



C. If possible, peel o£E the cortical portion from one stained 

 root and leave the central cylinder with the secondary roots 

 attached. Stain one section with iodine and sketch it. 

 Where is the starch of this root mainly stored ? 



D. Test some bits of parsnip for proteids by boiling them for 

 a minute or two with strong nitric acid. 



What kind of plant food does the taste of cooked parsnips 

 indicate? [Ow no account taste the hits which have been 

 boiled in the poisonous nitric acid.'] 



EXPERIMENT XIV 



Percentage of water in the plant body. Take any such soft portions of seed 

 plants as the roots of carrots or turnips, shoots of asparagus, and leaves of 

 lettuce or spinach, or cut off a green herbaceous plant at the level of the 

 ground. Slice the roots and stems as thin as possible and pick the leaves to 

 pieces. Weigh out convenient portions at once to avoid drying, place each 

 portion in a water bath, and heat until no further loss of weight takes place. 

 It will save much time and render the experiment more accurate if the 

 materials are in 'each case kept in a shallow vessel, such as a large watch 

 glass, throughout the process of diying and the weighings. Finally calculate 

 from the loss of weight the percentage of water originally present. 



EXPERIMENT XV 



What mineral substances are required by ordinary seed plants ? * * 

 A. Prepare a nutrient solution (No. 1) containing for every 1500 parts 

 by weight (grams) of water i the following amounts of salts : 



Grams 



Calcium nitrate 2 



Potassium chloride ■ \ 



Magnesium sulphate J 



Acid potassium phosphate (KHa PO4) J 



Ferric chloride solution a few drops 



Prepare several glass cylinders of the capacity of a pint or more by 

 rinsing out with strong nitric acid and then with plenty of water. 



1 Distilled water which has been prepared iu -a, glass, porcelain, or block tin 

 distilling apparatus and then aerated by shaking up with air should be used. 

 Very pure rain water collected from a thoroughly washed roof will answer 

 equally well. 



