FUNCTIONS OF THE KOOT. 209 



stem, the first-formed cells are subdivided, and then the sub- 

 divisions enlarge to the normal size, and this process goes on 

 while growth continues. All vegetable material is primarily 

 formed in the leaves or green parts of ordinary plants, and, 

 by a vital process of circulation, is transferred in a liquid 

 form to its proper destination. 



The seed is a minute plant, consisting of a radical or little 

 root, a terminal bud called the plumule, and one or more 

 seed-leaves, all snugly packed away in a shell for safe keep- 

 ing during transportation. In order that the sprouting plant- 

 let may be able to get hold of the earth for its water and 

 mineral supplies, and have substance enough to reach up into 

 the light and air where it is to find its future carbon, the seed- 

 leaves, or cotyledons, are formed of very condensed and com- 

 plex materials, — such as oil, sugar, starch and albuminoids. 

 The requisite conditions of germination for a sound, living 

 seed are air, water, and a moderate degree of heat. The 

 time intervening between the planting of a seed and the 

 appearance of the root varies from a few hours to many 

 months. It may be hastened in some cases by scalding the 

 seed for a few minutes in hot water, or by the judicious use 

 of a solution of camphor, sal-ammoniac, or oxalic acid. The 

 cotyledons of the squash-seed are pushed up into the air, 

 where they expand and thicken, assume a green color, and for 

 a time perform the functions of true leaves. 



The root is the first part of a plant to grow, and develops 

 downward, as if affected by the force of gravity. Light 

 neither hurts nor helps the root, but water is essential to its 

 life, and for this it penetrates the soil in every direction. It 

 is the special function of the root to absorb and furnish to the 

 rest of the plant, water, nitrogenous matter, and such soluble 

 minerals as each species requires for its use. For this pur- 

 pose it is admirably adapted by its peculiar structure, sub- 

 stance and mode of increase. The older portion of roots 

 serves to sustain the stem and hold it in place, and also acts 

 as a reservoir of supplies to the plant. The younger roots 

 usually branch off in an irregular manner, and elongate by the 

 multiplication of cells near their extremities. The tips of 

 roots are usually very minute fibres of exceedingly delicate 

 tissue, which insinuate themselves into the pores of the soil, 



27 



