1900] GEOTROPISM OF STEMS 187 
The conclusion, which has been anticipated, is that the 
response to gravity of the horizontal hypocotyl is always the 
same, whether the result is beneficial or, under artificial condi- 
tions, detrimental. Itisa response to local conditions in each 
individual zone of the hypocotyl, and is executed without the 
slightest regard to the relative positions of the different 
zones, or the serial parts of the plant, roots, hypocotyl, 
cotyledons. ; 
The pumpkin has even, figuratively, no brains. Its response 
to a stimulus is blind, like the instincts of animals: merely an 
effect, devoid in any individual instance of a purpose. As is 
often at least true of instinct, the response is not directly to 
the condition it is designed to correct, or to suit, but to some- 
, thing correlative, or merely concomitant. In response to a shift- 
ing of the pressure upon one another of the transverse elements 
of a tissue, the plant executes a change in its growth, which 
becomes of some service only when it results in a certain longi- 
tudinal arrangement of the plant-members; this longitudinal 
arrangement is the thing at fault, but the plant cannot perceive 
it. In nature the response meets the hidden purpose, but under 
changed conditions the same response is made, and is fatal. 
Certain flies flock at the scent of carrion, not in reality to gratify 
their peculiar esthetic sense, nor yet to get a meal, but because 
it takes them where their eggs will thrive; the Dictyophora 
panders to their instincts; the carrion flies revel in its slime, and, 
mistaking the attribute for the reality, deposit their eggs where 
they rot. The behavior of the pumpkin and the fly is essentially 
the same; both react blindly, but in nature, fortunately. 
A careful inspection of the table given above will show, in 
the different location of the region of greatest curvature in the 
Plants with encased roots and in those with encased cotyledons, 
- nice demonstration that each zone of the hypocotyl can act for 
itself. In the former the hypocoty]! is somewhat curved through- 
Cut, even in the most mature basal part, and most so about 4™ 
low the cotyledons, the upper, youngest part being almost 
straight ; while when the cotyledons were encased the curvature 
