HOW STEMS ELONGATE 



17 



season). The Irish potato is a stem: the 

 sweet potato is probably a root. 



46. HOW STEMS ELONGATE. Roots elongate 

 by growing near the tip. Stems elongate by 

 growing more or less throughout the young 

 or soft part or "between joints." But any 

 part of the stem soon reaches a limit beyond 

 which it cannot grow, or becomes "fixed;" 



and the new parts beyond 

 elongate until they, too, 

 become rigid. When a part 

 of the stem once becomes 

 fixed or hard, it never in- 

 creases in length: that is, 

 the trunk or woody parts 

 *--&* hi n ryroii' longi r or higher; 

 branches do not become far- 

 ther apart or higher front 

 tin (/round. 



47. The different re- 

 gions of growth in stems 

 and roots may be observed in seedling 



plants. Place seeds of radish orcal.bage 



between layers of blotting-paper or thick cloth. Keep 

 them damp and warm. When stem and tool have grown 

 an inch and a half long each, with waterproof ink 

 mark spaces exactly one-quarter inch apart. Keep the 

 plantlets moist Cora day or two, and it will be Pound that 

 on the stem some or all of the marks are mort 

 quarter inch apart : 

 <ii t he root t he marks 

 have not separated. 

 'I he root has grown 

 bej ond the lasl mark . 

 Pigs. 20 and 26. 



" 23 Rhl 



'.. old mullein 

 stalk, with 



strict li:il.it of 



growth. 



21. Excurrenl trunk. 

 A pine. 



1 1 ; i n o n e - 



li 



