266 



HOW CROPS GEOW. 



represented in fig. 46, wliich infests so many fanns. Each 

 node of the root-stock, being usually supplied with roots, 

 and having latent buds, is ready to become an independ- 

 ent growth the moment it is detached from its parent 

 plant. In this way quack-grass becomes especially troub- 



Fig. 46. 



lesome to the farmer, for, within certain limits, the more 

 he harrows the fields where it has obtained a footing, the 

 more does it spread and multiply. 



Suckers. — The rose, raspberry, and cherry, are examples 

 of plants which send out subterranean branches, analogous 

 to the root-stock. These coming to the surface, become 

 aerial stems, and are then termed sucker's. 



The Tubers of most agricultural plants are fleshy en- 

 largements of the extremities of subterranea,n stems. 

 Their eyes are the points where the buds exist, usually 

 three together, and where minute scales — rudimentary 

 leaves — may be observed. The common potato and arti- 

 choke are instances of tubers. Tubers serve excellently 

 for propagation. Each eye, or bud, may become a new 

 plant. From the quantity of starch, etc., accumulated in 

 them, they are of great importance as food. The number 

 of tubers produced by a potato-plant appears to be inn 

 creased by planting originally at a considerable depth, or 

 by " hillmg up " earth around the base of the aerial stems 

 during the early stages of its growth. 



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