PRACTICAL INFERENCES. 119 



sure 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 em- 

 ployed, 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 vege- 

 tative 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 pro- 

 duce flowers is enhanced by the high summer temperature 

 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 drought, or of a very low temperature, 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 possible short of frost, and 

 what is of even more importance, kept as uniform as pos- 

 sible. By such means the roots may be kept dormant, and 

 the waste to the farmer, which would occur from the un- 



