46 THE SEED AND ITS NEEDS 



and the weakest seedlings should always be pulled out and 

 discarded, and only those plants which have good vitality 

 should be retained and permitted to grow. 



Thinning is not only done to give the plants more room to 

 expand and to grow, but also to provide them with sufficient 

 space from which to gather plant food. It should therefore 

 be done as soon as possible, after the plants are up. The early 

 elimination of the surplus plants prevents any loss of the 

 available food. 



Thinning is accomplished in several ways according to the 

 crop : (1) By weeders or implements designed for the purpose 

 of cutting out the surplus plants; (2) by hand. Hand thin- 

 ning is usually practised on such plants as the garden beet 

 or the onion. 



Transplanting of Seedlings. — One of the principal reasons 

 for the transplanting of the seedling is to develop a good root 

 system. An ideal root system is one that has a great number 

 of short branches, bearing many small root hairs. Such a 

 root system provides a large area for the absorption of food 

 material in a comparatively small space. An expression for 

 this condition often used by gardeners is "ball of root," 

 which means a well-developed and compact root system. 

 The formation of this ball takes place only after the seedling 

 has been transplanted several times. It is formed when the 

 larger roots are broken off, which causes them to branch and to 

 make a number of small fibrous roots. The root system then 

 is a network of fine root hairs, all of which take food from the 

 soil. Such a root system is easiest and is most readily ob- 

 tained by the root pruning which takes place during trans- 

 plantings. With many plants repeated transplantings are 

 an advantage. The first transplanting is most important. 

 It consists in the pricking of the seedlings out of the seed 

 bed. Several precautions must be observed, of which the 

 most important one is the preparatory treatment of the seed- 

 lings before transplanting. A few days previous to the time 

 the plants are to be taken up, withhold the water supply 

 and ventilate the plants freely to harden the tissue of the 

 seedlings if they have been grown in a hotbed or cold frame. 

 An hour or two previous to the transplanting of the seedlings 



