Growth 343 



Describe the formation of leaves. From prepared slides study 

 and draw the growing tip in longitudinal section. 



From hand sections or from prepared slides study the secondary 

 thickening in the stem of sunflower, castor-bean, or other plant 

 of similar texture. Make some sections near the apex of the 

 growing shoot and some farther distant in order to follow the 

 development of inter-fascicular cambium and secondary bundles. 

 From prepared slides measure the extent of variation in the 

 growth of the seasonal rings. 



Adventitious organs. (Roots.) Follow the development of 

 adventitious roots upon cuttings of tomato, geranium, or grape. 

 In the case of tomatoes in fairly dry soil this is also conveniently 

 studied by binding to the stem at a node a ball of moist moss. 

 Germinate sunflower seeds and as soon as the radicle has emerged 

 about \ inch cut off the latter about \ inch from the coty- 

 ledons, place the cotyledonary portions on moss in a moist cham- 

 ber, and note the method of origin of the roots. 



(Buds.) Grow seedlings of flax in a saucer of sand or soil 

 until the hypocotyls have about reached full growth. Then cut 

 off the upper portion of the plant about \ inch below the coty- 

 ledons and discard the leafy portion. Cover the rooted hypo- 

 cotyls with a bell glass or tumbler to prevent drying out and 

 follow and describe the development of buds. Study the fleshy 

 root of sweet potato to ascertain if preformed buds are present. 

 Halve the root, place it upon moist sand under a bell glass, and 

 observe the development of shoots. Examine the leaves of 

 Bryophyllum calycinum for the presence of buds in the indenta- 

 tions of the margin. If no buds are found, place the leaves on 

 moist sand and observe occasionally. Follow likewise the 

 development of buds from a leaf of Begonia Rex, placing the leaf 

 upon moist sand with the petiole or a small part of the leaf slightly 

 covered. Sever a few of the larger veins, and protect the leaf 

 from drying out. 



Hot water forcing. During early winter or midwinter im- 

 merse for from 6 to 12 hours twigs of lilac (generally good) and 

 apple in a water bath controlled at a temperature of 35 C. Re- 

 serve some twigs untreated, or immerse them in water at 20 for 



