324 THE BIOLOGY OF THE PLANT 



How long is it ? At the tip look for the brown- 

 ish root-cap. How does it compare in length 

 with the growing end ? Judging from the facts 

 just learned, what do you consider to be the 

 principal differences between a root and a rhi- 

 zome 'i 

 Make a drawing of a single large root. 



3. The fronds. — How many does your specimen 

 bear ? To what extent do they vary in length? 

 Lay an entire frond on a flat surface. "What is 

 the shape of the outline ? What is the shape 

 of the rachis ? Color ? Size ? Is its surface 

 rough or smooth ? Does the rachis branch ? 

 How many pinnae does it bear ? Is the num- 

 ber constant ? What is their position with re- 

 gard to one another 1 How far above the sur- 

 face of the soil is the first pinna borne ? What 

 is the shape of a single pinna ? Size ? Is its 

 surface smooth? Compare with the rachis. 

 What variations in shape and size do you find ? 

 How are the pinnules arranged ? Do they vary 

 at all in number, shape, and size on different 

 pinnge ? Note the midribs of the pinnee. Do 

 the pinnules also have midribs ? If so, what is 

 their relation to those of the pinnae ? On which 

 side of the pinnules are the son borne ? Is this 

 an invariable position ? Do they have a defi- 

 nite arrangement ? If so, what is it ? Does 

 each pinnule have a constant number of sori? 

 Examine a number of fronds to find sori in 

 various stages of growth. What is the first in- 

 dication that a sorus is to be formed at a par- 

 ticular place ? What changes take place in it 

 during its development? What is the shape 



