128 



BOTANY. 



small string, and, holding one end of it just below one of 

 the lower leaves of your specimen, carry it up and around 

 the stem (Fig. 395), so that it shall pass just under each 

 successive leaf. Proceed in this way till you reach a leaf 

 standing directly over the one you started with. Your 

 string now includes what is called a leaf-cycle ; that is, 



FIG. 



394- 



the distance in a spiral line around the stem, from one 

 leaf to another placed exactly above it. 



Holding the string in place, observe, first, how many 

 times it has wound around the stem ; and, second, how 



