46 FOUNDATIONS OF BOTANY 



that show it, find out where the secondary roots arise. If possible, 

 peel off the cortical portion from one stained root and leave the cen- 

 tral cylinder with the secondary roots attached. Stain one section 

 with iodine, and sketch it. Where is the starch of this root mainly 

 stored ? 



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 show 

 them to contain ? [On no account taste the bits which have been 

 boiled in the poisonous nitric acid.] 



57. Storage in Other Roots. - - The parsnip is by no 

 means a remarkable plant in its capacity for root-storage. 

 The roots of the yam and the sweet potato contain a good 

 deal of sugar and much more starch than is found in the 

 parsnip. Beet-roots contain so much sugar that a large 

 part of the sugar supply of Europe and an increasing 

 portion of our own supply is obtained from them. Often- 

 times the bulk of a fleshy root is exceedingly large as 

 compared with that of the parts of the plant above 

 ground. 



The South African plant (Harp agopliy turn, Chapter 

 XXIV) is a good example of this, and another instance 

 is that of a plant, 1 related to the morning-glory and the 

 sweet potato, found in the southeastern United States, 

 which has a root of forty or fifty pounds weight. 



Not infrequently roots have a bitter or nauseous taste, 

 as in the case of the chicory, the dandelion, and the 

 rhubarb, and a good many, like the monkshood, the yellow 

 jasmine, and the pinkroot, are poisonous. Can you give 

 any reason why the plant may be benefited by the disgust- 

 ing taste or poisonous nature of its roots ? 



1 Ipomcea Jalapa. 



