THE WATER PATH IN PLANTS 107 
an outward direction as the tree becomes larger. The 
vessels formed in the bundle in spring and early summer 
are larger than those formed 
in late summer. When cut 
across in the tree these vessels 
look like pores. As all the 
bundles in the tree lie close 
side by side, the larger pores 
formed in the spring alternate 
each year with the smaller 

Fig. 142. Cross section of oak, show- ON€S and. forms a ring. One 
ee ring is usually made each 
year as the oak tree grows, so that 
the approximate age of the tree can 
be told from the number of the rings. 
The vascular bundles in a maize stem. 
If a young maize stalk was in the red 
ink, cut itacross. The red spots which 
mark the position of the bundles are 
arranged irregularly. If a fresh-grow- 
ing maize stalk is not at hand, take 
an old dried one. With a knite cut 
around and just through the outer hard Fie. 143. Vaseular 
layer. Then gently break it, pulling crnere ue ae 
apart the two ends at the same time. as ee 
As it breaks, the bundles pull out as stiff strings in the 

pith, and in this way the irregular arrangement is easily 
