10 PLANTS 



29. Compare the cotyledons of the seeds in regard to their behavior 

 during the early stages of development. 



30. Why does the primary root grow downward? To be determined 

 by experiment i. 



Experiment i. Spread a piece of moist white filter paper in the bottom 

 of a shallow plate or pan. On this set a bottle about three inches high 

 with a cork projecting from the neck. Fasten several pea seeds to the 

 cork with long pins in such a way that they will be suspended in mid-air 

 at least. an inch from the cork. The pins may be thrust through the 

 seed coats or the cotyledons but the caulicle and plumule must not be 

 injured. The seeds should be fastened so that the caulicle is directed 

 downward in one case, upward in another and horizontally in another. 

 Cover the whole with a bell jar and note the direction taken by the caulicle 

 when it germinates. Interpret the result. See paragraph 49. 



31. Why does the stem grow upward? To be determined by experi- 

 ment 2. 



Experiment 2. Seal up the hole in the bottom of a four inch flower pot. 

 Fill the pot with earth or sand and plant some pea seeds about an inch 

 below the surface. Moisten the soil and then cover the pot with wire 

 mosquito netting so that the earth will not fall out when the pot is in- 

 verted. Invert the pot and support it on an empty glass tumbler and 

 cover the whole with a tall bell jar. The tumbler should be set in a shallow 

 dish or pan on a piece of wet white filter paper. After a period of about 

 ten days, carefully raise the pot, allowing the soil to fall away and expose 

 the seedlings. Interpret the result. See paragraph 50. 



32. What changes occur in the cotyledons and what is their ultimate 

 fate? What is the function of the cotyledons? 



33. The young plant a. bean, b. pea, c. squash, d. corn. 



34. Reviewing development as if in a moving picture, describe the devel- 

 opment of the plumule. 



35. As in 34 describe the development of the caulicle. 



36. The hypocotyl is that part of the stem which develops from the 

 caulicle. Compare the hypocotyl of bean, pea, squash and corn. 



37. Root hairs (wheat). Study under glass cover. 



38. Draw root system of well developed bean. Note, primary, or tap 

 root, and, secondary, or lateral roots. 



39. The cotyledons are the first leaves. Are the leaves that develop 

 next like those of the mature plant? Are the third? Fourth? 

 Compare bean, pea and squash. 



40. Where do the branches appear? See also section viii. 



