Seeds and Their Germination. 21 



hypocotyl grow ? Look out for exceptions to any general 

 rule which you think you have discovered concerning the 

 relations between the growth of hypocotyl, plumule, and 

 cotyledons. 



EXERCISE 13. 



Beginning with the first exercise, read again all the pre- 

 ceding pages, and note as you come to them all the ques- 

 tions which you or your seedlings have not satisfactorily 

 answered. Try once more with the aid of new material and 

 new experiments, if necessary, to settle these undecided 

 questions. Perhaps some of your seedlings have not yet 

 had time to show what you wish to find out. Watch and 

 wait; see all that they do, and think why they do one 

 way rather than another.* 



EXERCISE 14. 



You have now learned that a caulicle has the nature of 

 both stem and root, and that a plumule is a bud which, like 

 other buds, is the beginning of a leafy stem. Your next 

 task is to discover the nature of cotyledons. Seedling buck- 

 wheats or morning glories may have already told you. 

 Squash, sunflower, castor-bean, and pine embryos will in 

 time tell the same story; but beans and scarlet runners try 



* If your work with beans in the jar is unsatisfactory, try again. S^ald the 

 jar and the stick by pouring in first a little warm water which you shake, then 

 hotter water, shaking again, and so on till the jar is gradually made hot; then 

 fill with boiling water and let it stand a few minutes. Fix beans on the stick as 

 you did in the first place, and dip them for ten or fifteen seconds in boiling water; 

 then put them in the jar with hot water not quite touching the lowest bean. 



