230 General Botany 



growth. Consequently the plants accumulate food more rapidly 

 and come into bearing earlier. 



Plants may be grown in a region where they would otherwise 

 perish by grafting them on other stocks. For example, the 

 vineyards of France were threatened with destruction by the 

 ravages of a root louse {Phylloxera) . American grape roots were 

 found to be immune to attacks of this insect, and the grape in- 

 dustry of France was saved by grafting the French vines on roots 

 of American grapes. In Florida it was found possible to extend 

 the cultivation of oranges farther north by growing the edible 

 orange on the roots of the Japanese bitter orange, which is quite 

 hardy. 



In testing apple seedlings for their possibilities as new varieties, 

 plant breeders take i -year-old stems and graft them into the 

 branches of a large, thrifty tree. As the tree has a large store of 

 carbohydrate food at hand, fruit may be developed and its value 

 determined on these cions the second or third year. To test the 

 seedHngs on their own roots would require perhaps from 10 to 15 

 years. In this instance grafting is used to hasten reproduction. 



When two varieties of apple are grafted together and the cion 

 does not make a perfect union with the stock, food may not pass 

 freely from the cion to the stock. This results in accumulation 

 of food above the point where the cion was set. The accumulated 

 food leads to increased growth and the formation of a thicker 

 trunk above than below the union. 



Sprout forests. With the exception of the California redwood, 

 cypress, and pitch pine, most conifers reproduce only by seed. 

 Redwood, poplars, oaks, chestnut, and many other broad-leafed 

 trees develop sprouts from stumps. Sprout forests, or coppice, 

 as foresters call them, grow more quickly because the sprouts 

 have a root system already established in the soil, while a seedhng 

 must first manufacture food and grow one. Chestnut coppice will 

 grow large enough to furnish railroad ties in 25 to 35 years, or 

 in about half the time required by seedlings. Sprout forests 



