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 (Harpagophytum, Chapter 
XXIV) is a good example of this, and another instance 
is that of a plant,’ 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 Ipomea Jalapa. 
e 
