

1901] GEOTROPISM OF STEMS 417 
and Cucurbita, with results unsatisfactory, but, so far as they 
showed anything, agreeing with those on Lupinus. 
Uninjured Cucurbita freed from its coats behaves at first 
exactly like Lupinus, but later the hypocotyl sometimes becomes 
concave below, even when the root tip has grown some centi- 
meters away from it. The behavior of these older Cucurbita 
hypocotyls is exceedingly various, but can in no instance be 
closely related to the positive geotropism of very young hypo- 
cotyls. Sometimes the hypocotyl becomes concave on the side 
where the peg forms, apparently under the peg’s influence.? 
This is not geotropism at all, though the concave side is nor- 
mally beneath, because the peg grows there. Later the stem 
may become concave below, next to the cotyledons, in an 
attempt to form the arch which in nature breaks through the 
ground, pulling the cotyledons after.*° This is real and fixed 
geotropism, not epinasty or nutation (unfixed geotropism). 
Frank, Véchting, and others have described similar behavior in 
the peduncles or pedicels of various plants. That it is not 
dorsiventrality in Cucurbita is shown by its occurring inde- 
pendently of the plane in which the cotyledons are placed. But 
they subsequently become erect on the clinostat. The curve in 
the other direction (negatively geotropic), described for Cucur- 
bita in the first of these studies, is also early evident. Double 
curves are very common, often about equaling each other and 
leaving the direction of the root unchanged. The whole subject 
is not really relevant here, and I leave it in the hope that prom- 
ised papers by Pollock * and Noll” will explain my diversity of 
results. 
The phenomenon which this paper describes shows anew 
that the structure of stems does not demand that the geotropic 
response they execute shall be negative, and that root structure 
° DARWIN and Acton: Physiology of plants, 193 fig. 38A. 
7? DARWIN and ACTON: /.c. fig. 388. 
™ Prelim. paper before Soc. Plant Morph. and Physiol. Dec. 1899. 
%2 Sitz. ber. Niederrhein Ges. f. Naturf. u. Heilkunde zu Bonn (S. A.) p. 3. 1900; 
also Jahrb. £. wiss. Bot. 34: 461. 1900 
