286 HOW CROPS GROW. 



too, the gardener molds a straggling, ill-shaped shrub or 

 plant into almost any form^he chooses ; for, by removing 

 branches and buds where they have grown in uiidue pro- 

 portion, he not only checks excess, but also calls forth 

 development in the parts before suppressed. Close 

 pruning or breaking the young twigs causes abundant 

 development of flower-buds on fruit trees that otherwise 

 "run to wood." 



Adventitious or irregular Buds are produced from 

 the stems as well as older roots of' many plants, when 

 they are mechanically injured during thfe growing season. 

 The soft or red maple and the chestnut, when cut down, 

 habitually throw out buds and new stems from the 

 stump, and the basket-willow is annually polled, or pol- 

 larded, to induce the growth of slender shoots from an 

 old trunk. 



Elongation of Stems.^— While roots extend chiefly 

 at their extremities, we find the stem elongates equally, 

 or nearly so, in all its contiguous parts, as is manjfest 

 from what has already been stated in illustration of its 

 development from the bud. 



Besides the upright stem, there are a variety of pros- 

 trate and in part subterranean stems, which may be 

 briefly noticed. 



Runners and Layers are stems that are sent out hor- 

 izontally just above the soil, and, coming in contact with 

 the earth, take root, forming now plants, which may 

 thenceforward grow independently. The gardener takes 

 advantage of these stems to propagate certain plants. 

 The strawberry furnishes the most familiar example of 

 runners, while many of the young ^shoots of the currant 

 fall to the ground and become layers. The runner is a 

 somewhat peculiar stem. It issues horizontally, and 

 usually bears but few or no leaves. The layer does not 

 differ from an ordinary stem, except by the circum- 

 stance, often accidental, of becoming prostrate. Many 



