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 secondaiy 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 (Harpagophytum, 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 Ipom&a Jalapa, 



