112 PLANT LIFE ON THE FARM. 



fibrous portions, and the requisite secretions are stored 

 the more readily in the roots. To ensure this rapid 

 growth, more essential in an annual crop like potatoes 

 than in those whose growth occupies part of two seasons, 

 a warm aspect and a well drained soil are essential, while 

 to ensure the formation of the secretions which render 

 the plant valuable, free exposure to light is also requisite. 

 Thus, hoeing and weeding owe their good effects not 

 only to the removal of useless plants occupying space 

 that might more profitably be employed, but they secure 

 to the crop freedom from the shade of the weeds, and 

 promote the access of light to the foliage and of air to 

 the roots. The excessive action of the vegetative organs 

 checks, to a varying extent, the development of the 

 fruiting organs ; indeed, the object of culture is to keep 

 the plant growing and to prevent its flowering. If the 

 seed of such plants is sown too early, growth is apt to be 

 slow, and woody fibre is produced where succulent cells 

 would be preferable, and, moreover, the tendency to 

 produce flowers is enhanced by the high summer tem- 

 perature which follows. If sown late, the growth of the 

 vegetative organs is, for a time, rapid, because the soil is 

 warmer and the sky lighter, while the tendency to form 

 fibre and flower is checked. 



The formation of subterranean tubers may be taken as 

 an indication that the plant prefers a period of rest. 

 The rest is, indeed, not absolute, but relative ; and while 

 little external change may be visible, it is probable, and 

 in some cases certain, that considerable chemical changes 

 go on during the period of apparent inaction. Under 

 natural circumstances the rest is secured, either by the 

 occurrence of heat and drouth, or of a very low tempera- 

 ture, the action of light being, in either case, excluded. 

 These facts supply hints as to the proper mode of storing 

 and pitting potatoes and roots. Moisture, light, and air 

 should be excluded, the temperature kept as low as pos- 



