THE RHEOTROPISM OF ROOTS 361 
at all, sensitive beyond 20™™ of their apex. In pre- 
s it has been shown that che rheotropic sensitiveness 
ma lly from the limit of the ion Since the 
7 rheotropic plants also, a ney area ten or more 
distant from the limit of the elongating zone, and therefore 
ssion of stimulus through a distance of twelve or more milli- 
m tissue that has ceased to elongate. 
heotropism is not confined to the primary root. Berg(/.¢.) 
‘s that he observed it in the secondary roots of eight species 
: ile it was absent in one species. My tests extended 
- Putting Berg’s results and mine together, 
$s with both primary and secondary roots have been 
theotropism of secondary roots. Of these eleven 
have shown themselves positive in both primary 
oots, two have shown themselves neutral in both | 
, and one (Tropacolum majus) was found sensitive | 
by Berg, but feebly sensitive in the primary and 
e etd roots by me. Bee maken 
ots. ae 
than the primary, but the euuiee an ; 
' ea mays (yellow dent) were more sensitive —— 
s — conclude at least that the second ry roots are 
ments of former investigators ot 
In igs lr u 
lo. in the ahiacerss of a plant t 
