128 ROOTS AND UNDERGROUND STEMS 



abled to keep their underground parts alive through the 

 supply of nourishment stored in their roots, and thus get 

 the advantage of their competitors by starting out in spring 

 with a good supply of food on hand. If you will dig 

 arbund any of our hardy winter herbs, such as the rib 

 grass (plantain), dandeHon, and common dock, that keep 

 a rosette of green leaves above ground all the year, you 

 will generally find that they have a more or less fleshy tap- 

 root full of nourishment, stored away underground. 



PRACTICAL QUESTIONS 



1. Compare a root of wild carrot with a cultivated one ; what diiFer- 

 ence do you see? 



2. Why are the fleshy roots of wild plants so much smaller than 

 those of similar species in cultivation? 



3. Why do farmers speak of turnips and other root crops as "heavy 

 feeders"? (180.) 



4. Which is most exhausting to the soil, a crop of beets, or one of 

 oats? Onions, or green peas? 



5. Which is best to succeed a crop of turnips on the same land, hay 

 or carrots? 



6. Write out what you think would be a good rotation for four or 

 five successive crops. 



7. Study the following rotations and give your opinion about them ; 

 suggest any improvements that may occur to you, and give a reason for 

 the change : Beets, barley, clover, wheat ; cotton, oats, peas, corn; oats, 

 melons, turnips ; cotton, oats, corn and peas mixed, melons ; cotton, 

 hay, corn, peas. 



SUB-AERIAL ROOTS 



Material. — A hyacinth bulb or a cutting of wandering Jew grown 

 in a glass of water. Specimens of any kind of parasitic plants that can 

 be obtained, such as mistletoe, dodder, resurrection fern {Polypodium 

 incanum), etc. Freshly rooted cuttings of geranium, coleus, or other 

 easily rooting twig, 



182. Subterranean and Sub-aerial Roots. — The roots we 

 have been considering are all subterranean and bring the 

 plant into relation with the earth, whether for purposes of 

 nourishment, or of anchorage to a fixed support, or, as in 

 the majority of cases, for both. But many plants do not 

 get their nourishment directly from the soil, and these give 



