XV. 



SPOXGIQLES. 



f MHE tips of growing roots are usually covered 

 with a mass of loose cellular tissue which was 

 formerly called a spongiole, and was supposed to 

 be the chief agent in the absorption of fluids from 

 the soil. It is now known that this is not its func- 

 tion, and that its chief office is to protect the deli- 

 cate extremity of the root as it pushes its way 

 through the soil. In 1857, Mr. A. Tre"cul gave the 

 name "pileorhiza," meaning root-cap, to this organ, 







which indicates its appearance and office. In 1837, 

 Ohlert showed that if this so-called spongiole be 

 cut off from a young root, and the wound covered 

 with water-proof varnish, absorption takes place 

 quite as well as before the operation; he expressed 

 the opinion, now well established, that the chief 

 organs of absorption are the numerous delicate 

 hairs which occur a short distance back from the 

 apex. The following is from the pen of Dr. W. J. 

 Beal, of the Michigan Agricultural College, on this 

 subject: "The tips of growing roots are often 

 called spongioles or spongelets. Their name 

 originated about one hundred and forty years ago, 



(102) 



