100 



INTRODUCTION TO BOTANY 



If the terminal bud of the spur contains leaves as well as 

 flowers, a leaf bud is likely to grow in the axil of one of the 



leaves and thus provide for the growth 



of the spur during another year. This 



process may go on for a good many years. 

 Evidently, when the spur produces a 



terminal bud containing flowers, it cannot 



grow straight ahead 



but must turn aside 



somewhat. A lit- 

 tle study of the 



age of fruit spurs, 



made by cutting 



across them and 



counting the rings 



of growth, shows 



that they increase 



in length very 



slowly. This must 



be the case, since 



much of the plant 



food used by the 



spur is expended 



in producing the 



flowers and fruit. 



The flower scars 



on an old fruit spur are not all alike, 

 some being much larger than others. 

 This is because the smaller ones mark the 

 places where flowers were borne but no 

 full-grown fruit was matured, while the 

 ones that bore successful fruit are larger 

 and more sharply defined. 



What would be the effect on the 

 growth of a young tree if all the fruit spurs or buds that 

 produce them were pruned away year after year? 



FIG. 85. A lengthwise 



section of bud of thorn 



tree (Cratcegus) 



br, brown outer bud 

 scales ; o, pale bud scale ; 

 i, innermost rudimentaiy 

 leaves ; g, growing point 

 at apex of twig, consisting 

 of cells in a condition to 

 sub-divide and multiply 

 rapidly at the beginning 

 of the growing season. 

 Somewhat magnified 



FIG. 86. Twig of cotton- 

 wood with buds in winter 

 condition 



b.sc, bud-scale scars. Two 

 thirds natural size 



