THE GROWTH OF THE PLANT 85 



food need not necessarily come from without. An ex- 

 amination of any seed always reveals a supply of food- 

 stuff either in the embryo itself, or packed around it. 

 In the seeds suggested as types, the broad-bean, French- 

 bean, and sunHower store food-material in the cotyle- 

 dons of the embryo ; in the case of the maize the 

 food-material is stored in the endosperm which sur- 

 rounds the embryo. 



An experiment can now be made to find out whether 

 the growing seedling uses the food that has been stored 

 up in the seed. 



Experiment 53 



Aim. — To find out whether a growing seedling uses 

 the food that is stored up in the seed. 



Method. — Three French-beans are planted. One (a) 

 is allowed to grow naturally. In the case of the second 

 seedling (b) the cotyledons are cut through at the base 

 as soon as they are sufficiently above the surface of the 

 earth to admit of the cut being made without injury to 

 any other part of the seedling. When the cuts have 

 been made and the cotyledons thus disconnected from 

 the rest of the plant, it is better not to attempt to 

 remove them, as such removal would probably cause 

 injury to the shoot or root of the young plant. The 

 cotyledons are cut off from the third seedling (c) as 

 soon as the first foliage leaves have expanded. 



Observations. — The results noted are, that 



(a) grows and develops ; 



(b) quickly withers ; 



(c) is not affected by the removal of the cotyledons. 

 Fig. 40 is a photograph of two French-bean seedlings 



growing under similar conditions in one pot. From one 

 of the seedlings the cotyledons were removed as soon as 

 that operation was possible without injitry to the rest 

 of the seedlings. Up to that time the seedhngs were 

 equally healthy. 



Inference. — The seedling uses the food stored in the ■ 

 seed until the unfolding of the green leaves enables it 

 to build up food substances for itself. 



