360 BOTANICAL GAZETTE [May 
roots of Helianthus annuus and of Brassica alba, ten positive curves 
in a total of eighteen roots were obtained. The other eight 
roots all remained straight. The relatively small proportion of 
curves was doubtless due to the shortness of the period of the 
experiments and to the technical difficulties involved in the 
method. By shielding from the water stream by a glass tube 
the whole root of Zea mays (popcorn) except the apical 1.5 to 
2™™, fifteen positive curves and sixteen straight roots resulted. 
Unfortunately the periods of the experiments for this plant were 
only from 4 to 8 hours. Had they all extended to 12 hours 
there would doubtless have been a much larger proportion of 
curves. The absence of any negative curves, however, shows 
that the curves obtained were really rheotropic. The apical 0.5 
to 1.5" of the root of Raphanus sativus exposed to the water 
stream by the same method as used with Zea mays (popcorn) : 
_ gave thirty positive curves and nine straight roots ina total of - 
thirty-nine seedlings. In two of these experiments there on 
nev more than 1™™ of root tip exposed to the current, yet even 
case more than half the roots became positive. Tt mi 
ed, therefore, that the rheotropic sensitiveness of a vey: tee 
thas been demonstrated. - 
the root of Vicia sativa is “yheoteopiae ensit 
out its elongating zone was indicated, but n demon- 
by the experiments of Juel (/.¢.). He employed 
ec lings, especially in the case in which 7 to ge 4 
oot Sowers, and | ten gave positive curves. ae 
in teen seedlings of Raphanus had 20™ of the apex < of 
vered, only seven very weak positive curv: 
ere were four weak negative curves, and eight 
7 be said. therefore, that the roots of ggg 8 
