REDUCED ABSORPTIVE SURFACE OF BLUEBERRY ROOTS. 



41 



even when enlarged 5,000 diameters. Notwithstanding the fact, 

 therefore, that the blueberrj^ roots are fine and numerous, their 

 actual absorptive capacity would appear 

 to be small, in consequence of the absence 

 of root hairs. 



It is found by a computation that a sec- 

 tion of a blueberry rootlet having no root 

 hairs presents about one-tenth the absorp- 

 tive surface of an equal area of a wheat 

 rootlet bearing root hairs, and the thick- 

 ness of the surface membranes in the 

 wheat is certainly not more than a quarter 

 that in the blueberry. Furthermore, the 

 blueberry rootlet grows only about 0.04 inch (1 mm.) a day under 

 favorable conditions, while the wheat rootlet often grows twenty 

 times as fast. In all this provision for rapid food absorption in the 

 one plant and retarded absorption in the other we find a reason for 



Fig. 14. — Root of a blueberry 

 plant. (Natural size.) 



Fig. 1.5. — Rant of a blueberry plant. 

 10 diameters.) 



(Enlarged 



Fig. 1G. — Blueberry rootlet. 

 (Enlarged 100 diameters.) 



the comparatively very slow rate of stem growth that characterizes 

 the blueberry plant. The importance of slow root absorption and 

 the danger to which these plants would be subjected if their roots 

 absorbed water rapidly are discussed on page 50. 



193 



