A MANUAL OF BOTANY 37 



Study of forms. Examine the rosettes and observe the 

 arrangement and varying size of tlie leaves. Why do such 

 conditions exist? Why do so many plants have rosettes 

 that persist through the winter? How are they preserved 

 from injury from the winter cold? Bietiuials and ivinter 

 annmds commonly possess rosettes. What are such plants? 

 Examine, in particular, the winter rosettes of the mullein 

 and look at the covering of the leaves. What is it? Ex- 

 amine (ni and Ip). Wliat may this covering be for? Make 

 careful drawings of rosettes, showing outline of the whole 

 and details of one leaf. Draw hairs of mullein (m and Iji). 



Examine a growing plant that has for some time been in 

 a window. What position do the leaves occupy with refer- 

 ence to the window? What is the cause of this condition? 

 How are the large and small leaves arranged ? Why is such 

 an arrangement called a mosaic .? What benefit does the 

 plant receive from such an arrangement? Kecall if you 

 can the appearance of ivy leaves or plants climbing over 

 brick and stone walls. Look in your reference books for 

 pictures showing leaf mosaics. Make a drawing showing 

 leaf mosaics. 



Arrangement on stem. Examine growing leafy shoots for 

 the leaf arrangements, comparing them with the bud ar- 

 rangement already learned, and name in a similar manner. 

 Look down the shoot with the apical portion toward you, 

 and observe the position of the leaves, radiating outward. 

 What agent decides the leaf position? Make a diagram 

 showing the leaf position as a result of the last observation. 



5. Leaf Modifications 



Material. Thistles, cacti, cobaea, vetch, smilax, pitcher 

 plant, locust, and head cabbage, besides many other plants 

 easily obtained, will furnish leaf modifications in abun- 

 dance. 



