388 



HOW CROPS GROW. 



as they are appropriately named, scales or rudimentary 

 leaves are seen, and thence roots proper are emitted. In 

 the axils of the scales may be traced the buds from which 

 aerial and fruit-bearing stems proceed. Examples of 

 the root-stock are very co||^mon. Among them we may 

 mention the blood-root and pepper-root as abundant in 

 the woods of the Northern and Middle States, various 

 mints, asparagus, and the quack-grass {Agropyrum* 

 repens) represented in Fig. 46, which infests so many 

 farms. Each node of the root-stock, being usually sup- 

 plied with roots, and having latent buds, is ready to 

 become an independent growth the moment it is detached 



Fig. 46. 



from its parent plant. In this way quack-grass becomes 

 especially troublesome, for the more the fields where it 

 has obtained a footing are tilled the more does it. com- 

 monly spread ahd multiply; only oft-repeated harrow- 

 ing in a season of prolonged dryness sufiSces for its 

 extirpation. 



Corms are enlargements of the base of the stem, bear- 

 ing leaf-bnds either at the summit or side, and may be 

 regarded as much-shortened rhizomes, with only a few 

 slightly-developed intern odes. Externally they resemble 

 bulbs. The garden crocus furnishes an example. 



Tubers of many plants are fleshy enlargements of the 



♦ Formerly Trlticum. 



