A SEED AND ITS GROWTH 



55 



What are the cotyledons for? Let us study this from a 

 couple of the beans which we have kept from an earlier 

 experiment, and which are growing either in the same tum- 

 bler or in separate ones. Their large cotyledons show just 

 below the leaves^ The younger the plants are, the better 

 for the experiment. Carefully cut away the cotyledons 

 from one plant, but leave the other untouched. If you 

 have three plants, take a single cotyledon from the third. 

 Then keep the plants watered exactly alike, and watch to see 



FIG. 34. Pea seedlings. The cotyledons stay underground. 



which thrives the best. The one with no cotyledons does 

 poorly, the one with both does well, and the third is midway 

 between the two. Now what do you think is the duty of 

 the cotyledons ? 



It ought to be plain, then, that in the last experiment with 

 deeply planted seed the corn and peas did better than the 

 radish and tomato, not only because they were larger, but 

 also because they got much greater help from their cotyle- 

 dons. The seed-leaves of the others were too small to do 

 any such service. 



The experiment would not have come out quite so well if 

 beans had been used. We have probably already noticed 



