Life of Plants and Animals 205 



The formation of the embryo was the result of the 

 fertilization of the flower in which the seed was pro- 

 duced. 



So long as the seed remained dry the starch, or 

 albumen, as it is also called, remained unchanged, 

 being insoluble as starch (recall Experiment I, c). 

 Hence it could not be used as food by the embryo. 

 As soon as the seed, however, is soaked or placed in 

 moist earth of sufficiently high temperature, water 

 enters the seed (recall Experiment VI, 6), causing it to 

 swell, and the starch is partly changed into sugar, 

 giving the seed a sweetish taste. 



The sugar is soluble (Experiment I, c), and is gradu- 

 ally absorbed by the little embryo, which has slowly 

 awakened from its sleep because of the stimulating 

 effect of heat and moisture. The taking in of this 

 sugar, as boys and girls sometimes do, enables the 

 little embryo to grow. As it grows it becomes too 

 large for the original seed-coats; and, consequently, 

 causes them to burst somewhat as a growing crayfish 

 causes his shell to split or a chick causes its egg- 

 shell to crack. Its root lengthens out and turns away 

 from the light; the tiny leaflets of the plumule increase 

 in size; the stem lengthens and carries the leaves 

 upward towards the light, the leaves being green 

 from the presence of a coloring- matter (chlorophyl), 

 the roots being pale white and covered with tiny root- 

 hairs. 



While this unfolding of the embryo has been going on, 

 the original food supply has been diminishing, till 

 nothing scarcely but the seed-coats remain. The 

 little plant must now adopt a new method of obtaining 

 food. Like the chick just hatched, it must now begin 

 to find its own food. This it does by means of its roots 

 and root-hairs in the soil. 



PHYSIOLOGY OF ABSORPTION AND CIRCULATION. 

 In the soil, surrounding the root, more or less mois- 



