no 



SEEDS AND SEEDLINGS 



149. Root Hairs are the chief agents in absorbing mois- 

 ture from the soil. They do not last very long, but are 



constantly dying and being formed again in 

 the younger and tenderer parts of the root. 

 These are usually broken away in tearing 

 the roots from the soil, so that it is not 

 easy to detect them except in seedlings, even 

 with a microscope. In oat and maple seed- 

 lings they are very abundant and clearly 

 visible to the naked eye. The amount of 

 absorbing surface on a root is greatly in- 

 Seediin crease d by the presence of the hairs ; and 



of wheat, with they exude, moreover, a slightly acid secre- 

 tion, which aids them in dissolving and 



absorbing the mineral substances contained in the particles 



of earth and sand to which they adhere. 



150. The Root Cap. Look at the tip of the root through 

 your lens and notice the soft, transparent, 



crescent or horseshoe-shaped mass in which 

 it terminates. This is the root cap and 

 serves to protect the tender parts behind 

 it as the roots burrow their way through 

 the soil. Being soft and yielding, it is not 

 so likely to be injured by the hard sub- 

 stances with which it comes in contact as 

 the more compact tissue of the roots. It 

 is composed of the loose cells out of which 

 the solid root substance is being formed, 

 and the growing point of the root is at the 

 extremity of the tip just behind the cap 

 (Fig. 245). The cap is very apparent in 

 a seedling of corn, and can easily be seen 

 with the naked eye, especially if a thin 

 longitudinal section is made. It is also 

 well seen in the water roots of the common c > root ca P: 

 duckweed (Lemna\ and on those developed gr wing P im ' 

 by a cutting of the wandering Jew, when placed in water. 

 Are there any hairs on the root cap? 



