STEMS 17 



25. The shape of the stem. — No two plants have their stems 

 shaped exactly alike, and the differences are so great in all spe- 

 cies of fruit that they are of considerable importance in classi- 

 fication. As an example, the trunks of old apple-trees may be 

 studied ; it will be noted that they are usually buttressed at the 

 base; the trunk is seldom a perfect cylinder; it is ribbed and 

 ridged as is the trunk of no other tree. The trunks of all other 

 tree-fruits have similar marks of recognition, which often ex- 

 tend to varieties. The stems of some species of Rubus, Ribes, 

 and Vitis may be circular, of others polygonal, or they may be 

 fluted or channeled, or a cross-section may show more or less 

 prominent angles. The internodes on branches of the tree- 

 fruits are commonly considered cylindrical, but usually they 

 are cylinders with more or less conical ends. Neither are the 

 cross-sections of these internodes always circular. Whether the 

 branches are straight or otherwise often constitutes a fine mark 

 of distinction in some of the fruits; very frequently the inter- 

 nodes zigzag. 



26. The branching" of stems. — The primary shoot of a plant 

 is a single stem, and in some cases may so continue, but in the 

 cultivated fruits branches or secondary axes arise from buds on 

 the primary or central axis; the secondary axes may in their 

 turn bear branches or tertiary axes and so on. There may, 

 therefore, be few or many branches on any of the fruiting 

 plants wdth which pomology is concerned. The angles at which 

 these branches arise from their axes give shape to the tree, 

 making it upright, spreading, open-topped, dense, round-topped, 

 vase-formed, and so on. 



27. Fruit-spurs. — All of the tree-fruits, and the currant and 

 gooseberry as well when the fruiting age comes on, bear short 

 much reduced branches which grow very little from year to year 

 and seldom reach a length of more than a few inches. These 

 reduced branches are spurs or fruit-spurs (Fig. 10). They are 

 easily recognized by the few or many scars which mark the place 

 where buds have fallen from year to year. There are great 

 differences in the age which fruit-spurs attain and in their 

 numbers and position on fruit-plants. Some spurs, as those 

 of the apple and pear, live many years ; they persist longer on 

 red than on black currants ; some varieties of plums and cherries 



