CHAPTEE V 



ROOTS 



63. General character. — The root is a third prominent 

 plant organ, and it presents even a greater variety of rela- 

 tions than leaf or stem. In whatever relation it is found 

 it is either an absorbent organ or a holdfast, and very often 

 both. For such work no light-relation is necessary, as in 

 the case of foliage leaves ; and there is no leaf-relation, as 

 in the case of stems. Roots related to the soil may be 

 taken as an illustration. 



It is evident that a soil root anchors the plant in the 

 soil, and also absorbs water from the soil. If absorption is 

 considered, it is further evident that the amount of it will 

 depend in some measure upon the amount of surface which 

 the roots expose to the soil. We have already noticed that 

 the foliage leaf has the same problem of exposure, and it 

 solves it by becoming an expanded organ. The question 

 may be fairly asked, therefore, why are not roots expanded 

 organs ? The receiving of rays of light, and the absorbing 

 of water are very different in their demands. In the former 

 case a fiat surface is demanded, in the latter tubular pro- 

 cesses. The increase of surface in the root, therefore, is 

 obtained not by expanding the organ, but by multiplying 

 it. Besides, to obtain the soil water the roots must burrow 

 in every direction, and must send out their delicate thread- 

 like branches to come in contact with as much soil as pos- 

 sible. Furthermore, in soil roots absorption is not the only 

 thing to consider, for the roots act as holdfasts and must 

 grapple the soil. This is certainly done far more effectively 



ap 



