SEEDS 



79 



After sending down a root the hypocotyl began 

 to develop into a strong stem which crooked itself 

 until it reached the surface of the soil and then 

 pulled the cotyledons or seed-leaves after it (Fig. 

 42). These turn green and after a time shrink and 

 fall off. 



The pea cotyledons were left down in the soil, 

 the epicotyl alone pushing up to the surface. The 

 corn pushed a slender growing point to the surface 

 leaving the cotyledon and endosperm behind in the 

 soil but still attached to the little plant (Fig. 43). 



USE OF COTYLEDONS AND ENDOSPERM 



Experiment. Plant some beans in a pot or box 

 of soil and as soon as they come up cut the seed- 

 leaves from some of them and watch their growth 

 for several days. It will soon be seen that the plants 

 on which the seed-leaves were left increase in size 

 much more rapidly than those from which the seed- 

 leaves were removed (see Figs. 43 and 44). Sprout 

 some corn in the seed tester. When the seedlings 

 are two or three inches long, get a wide-mouthed 

 bottle or a tumbler of water and a piece of paste- 

 board large enough to cover the top. Cut a slit 

 about an eighth of an inch wide from the margin 

 to the centre of the pasteboard disk. Take one of 

 the seedlings, insert it in the slit, with the kernel 

 under the pasteboard so that it just touches the 

 water. Take another seedling of the same size, 

 carefully remove the kernel from it without injur- 



