SEEDS AND SEEDLINGS 



35 



52. Food in seeds. The concentrated food found in the 

 seeds of all plants is of interest to us in three ways : First of 

 all, we may infer that this food is actually used by the young 

 plant until such time as it is able to provide for itself. That 

 this is a sound inference may be tested by separating from 

 several seedlings the " food reserve." Next, we can observe 

 that the cotyledons in such plants as the beans and peas do 

 actually shrivel away as the plant becomes larger ; and that the 



_ K g 



FIG. 8. Young plants emerging from seeds 



On the left, squash; on the right, bean. In the squash a little outgrowth on the 



hypocotyl keeps the seed coat in place while the cotyledons are carried aloft. C, C, 



cotyledons ; E, epicotyl ; H, hypocotyl ; gg, ground line 



contents of the corn grain also disappear as the seedling de- 

 velops. Finally, by means of chemical experiments we can see 

 that the changes taking place in the " food masses " of the 

 seedlings are of the kind we should expect to find if the 

 food were actually being transported to the growing portions. 

 (See p. 79.) 



A second question that may arise is that of the origin of the food 

 which we find in the seeds. It is enough for the present to consider 

 that, as the developing seed obtained the materials for its growth from 

 the parent plant upon which it originated, the reserve food that we 

 find within the coat of the seed was probably also obtained from the 



