12 NATURE TEACHING 



condition, and with some which have merely been soaked 

 for a few hours in water to soften them. 



On examining the grains, the embryo or " germ " 

 may be seen as a white patch lying on one side of the 

 grain near the pointed end ; in the case of those grains 

 which have been soaked, the embryo can be readily 

 detached from the rest of the seed. The seed is mono- 

 cotyledonous, and careful examination of the detached 

 embryo shows that the single cotyledon does not grow 

 or extend through the seed-coat, but forms the means of 

 communication through which the reserve of plant food 

 passes into the young growing plant. The cotyledon, 

 here known as the scutellum^ lies upon the surface of the 

 albumen, which in these seeds consists almost entirely 

 of starch. As soon as germination begins, the scutellum 

 secretes a digestive fluid which converts the insoluble 

 starch into soluble substances, which are readily absorbed 

 by the scutellum and" passed on to the growing plantlet, 

 lying on, and attached to, the other side of the scutellum. 

 As the starch is dissolved and used up, the scutellum 

 presses forward into the vacant space, finally taking up 

 all the starch and leaving the seed-coat empty. While 

 this is going on, the young plant is growing in size, 

 thrusting its roots into the soil and its leaves into the 

 air, so that by the time the supply of starch within the 

 seed is exhausted it is able to obtain its own food. 



PRACTICAL WORK 



The following exercises are suggested in illustration 

 of the principles already discussed ; they may be per- 

 formed by the pupils themselves or by the teacher, and 



