THE RHEOTROPISM OF ROOTS. 
FREDERICK C. NEWCOMBE. 
{WITH FIFTEEN FIGURES) 
(Concluded from p. 283.) 
VI. LOCATION OF THE SENSITIVE AREA. : 
___ SEVERAL experiments were made by Juel™ to locate the sen- 
_ Sitvearea. His tests were of two kinds. He cut off the apical 
‘Asm of the root of Vicia sativa, exposed the seedlings thus pre- 
: pared to the water current, and found that rheotropic curves fol- 
‘owed somewhat more promptly and with greater angles than in 
“unjured roots. So many seedlings were employed, and the 
‘Sponses were so uniform, that we are probabably justified in 
accepting the results as demonstrating a rheotropic sensitiveness 
of the foots in the absence of the apex. Juel’s other device - 
‘msisted in covering the apical portion of roots with capsof = 
, These caps varied from 2 to 7 or 8™™ in length. oe 
“lent experiments were made with the shorter caps to show — 
. the root was sensitive throughout its elongating zone. With = 
re, 7 to 8™™ long only six roots were tested, and of these — 
| 1. Experiments with water-jets. oe 
wee first series of experiments to determine the extent a a j 
a area was made by the employment of fine ct 
a aaa Various small areas of the root. Each seedling é 
i wy by wet cotton ina perforation in a cork TE 
sedi hy of a short glass cylinder 1.5 to 3™ 10 age i 
ee thus Projected both above and below the © a wes 
Part was packed in wet cotton, while 5 to 17 A : 
1 oMsuchungen iiber den Rheotropismus der Wurzeln. Jahrb. _— 
