1904] NEWCOMBE & RHODES: CHEMOTROPISM OF ROOTS Kis. 
The particular attractive component of the salt is not shown. 
It may be either the sodium or the phosphoric acid ion. Recalling 
the work of Stange™ and of Buller™s one might think the response 
to be due tothe PO, ion. Experiments now being made in this 
laboratory will, it is hoped, determine this question. 
The general indifference of the roots of Cucurbita Pepo toward 
the chemicals used indicates that we may expect further study of 
the chemotropism of roots to show the same specific differences 
in sensitiveness to chemicals as is shown in sensitiveness toward 
light; that is, there will be found chemotropic and non-chemo- 
tropic roots. 
The behavior of all the roots tested gives no indication of 
osmotropism. Lupinus albus was indifferent to the one-sided 
application of a 3.5 per cent. solution of cane sugar, and the 
same plant gave no negative bends when a solution of the 
di-sodic phosphate concentrated enough (four atmospheres) to 
cause death was applied to one side only. Yet the roots of this 
plant are hydrotropic. The roots of Cucurbita Pepo were indiffer- 
ent when chemicals plus the gelatin gave osmotic pressure of 
about 78° of the mercury on one side and 170™ of mercury on 
the other. 
From Rothert’s’® view one would bisa osmotropism and 
hydrotropism as identical; yet it is not improbable that roots 
will be found which are not osmotropic though they are hydro- 
tropic. Such is the indication in these experiments. 
The behavior of the lupin roots in curving away from all 
chemicals used except the sodic salt, may be either traumatropic 
or chemotropic. Or may this not be a reaction where chemo- 
tropism and traumatropism lose their distinction ? 
UNIVERSITY OF MICHIGAN. 
™STANGE: Bot. Zeit. 48: 124. 1890. 
*SBULLER: Annals of Botany 14: 558. 1900. 
16 ROTHERT: Flora 88: 415. 1901. 
