THE STEM AND THE LEAF 



59 



going to outstrip the corn, but if they are kept down until the 

 corn has begun to shade the ground well, there will be little 

 further trouble from 

 most weeds. If, how- 

 ever, the corn is cut 

 early for green fodder 

 or for ensilage, a rank 

 crop of weeds will 

 spring up between 

 the rows. So foxtail 

 and other weeds be- 

 gin to flourish among 

 the stubble as soon 

 as oats, wheat, or rye 

 have been reaped. 



The stem, then, by 

 lifting the leaves up 

 into the sunlight and 

 supporting them there 

 in favorable positions 

 (fig. 39), gives them 

 a chance to do pho- 

 tosynthetic work, so 

 that the whole plant 

 prospers. Even climb- 

 ing plants like the 

 English ivy (fig. 40), 

 with stems that bend 

 away from the light 

 toward a supporting 

 rock or tree trunk, 

 turn their leaves to 

 face the light. There 

 are many plants 

 creeping kinds, like white clover, and those with flattish clus- 

 ters of leaves, like the dandelion which flourish in places 



W 



FIG. 40. An English ivy (Hedera) grown in 

 front of a south window 



WW, the line of the window casing ; all to the left 

 of this is unlighted wall. The tips of the shoots (t) 

 avoid the light ; the young leaves (I) have assumed 

 no definite position ; the mature leaves are nearly 

 at right angles to the light coming from the direc- 

 tion of the arrow 



