C4 LESSONS IN CHEJIISTRY. 



directions. One of these is to become the root, and the other 

 the stem of the future plant. 



83. This is the beginning of the work and in the fir^t 

 stage the ingredients of the soil in which it is placed contri- 

 bute nothing to its growth. In the seed itself there is laid 

 up a supply of all the earthy matters which are for some time 

 required. Daily, however, the young plant increases in size, 

 its colour as it approaches the surface becomes of a greener 

 hue, the root pierces deeper into the soil and minute hair-Hke 

 fibres branch off from it, leaves covered on their surface with 

 innumerable pores or mouths unfold themselves on the stem, 

 and it now begins to condense within its structure the 

 gases with which the air surrounds it, and to convert them 

 into wood, starch, and the various compounds which we 

 lately described. Next the flower comes, and following it 

 the fruit and seed, and then in the commonly cultivated 

 annual* crops the work which the plant was produced to ac- 

 complish being finished, the wheels cease to go on, and neither 

 sun nor soil can stimulate them to new motions. The mature 

 seeds, if not gathered by the husbandman, are deposited in 

 the earth or dispersed by the winds. The plant withers and 

 dies, and the dead matter undergoes a series of changes by 

 which it restores to the soil and the atmosphere the materials 

 which, for a time, had been abstracted by the living vegetable 

 and confined within its substance, f 



84. As it will be required frequently to refer to the ofiices 

 performed by the organs of plants, it mil be necessary briefly 

 to describe their structure. 



Every farmer is familiar with the parts of which a tree 

 consists, he knows that a root binds it firmly to the soil, that 

 a stem covered with a hark rises up into the air, and that 



' Annual plants are those which ripen and die in the course of one 

 year. Biennial plants are those which, like the carrot, produce leaves 

 the first year, and in the second ripen their seeds and die. Perennial 

 plants are those which like trees live for a number of years. 



f Seeds may be kept for a considerable time uninjured, but the different 

 species vary very much in this respect; thus, wheat has germinated 

 after 100 years (Pliny), and rye after 140 years (Home), while the 

 seeds of coffee cannot be kept any time without risk. Every year the 

 ' loss to the farmer from seeds unsound, from bad preservation and other 

 causes, is enormous; and, when we take into account the impositions 

 practised by unprincipled dealers, we may fairly assume, that on the 

 average, more than one half of the seeds sown in this country are lost. 



