242 BOTANICAL GAZETTE [SEPTEMBER 
such terms as “‘duplicate of type,” ‘‘co-type,” ‘type locality,” 
etc., and suggested that some action be taken looking towards an 
agreement as to what should constitute a type specimen. 
F.C. NewcomsBe: Kheotropism and the relation of response to 
stimulus.—It has been shown by Strasburger and Stahl that 
plasmodia of Myxomycetes grow against a gentle stream of 
water. Jonsson found three fungi and the roots of three 
phanerogams that also grew either against or with a stream of 
water. For this phenomenon Jonsson proposed the term 
rheotropism. As the work was left by Jonsson there was no indi- 
cation of the extent of rheotropism among phanerogams, nor 
was it determined whether there were any negatively rheotropic, 
nor whether there were any indifferent roots, since the three 
species cited by this author were positively rheotropic. 
The work which is reported in this paper has shown that 
among seventeen species of monocotyledons and dicotyledons 
studied eight are positively rheotropic and nine are indifferent 
or neutral. None have been found to be negatively rheotropl 
Only seedlings were used. 
The phenomena of rheotropism in roots are these. When 
seedlings are suspended with their roots dipping into water 
flowing with a favorable velocity, the roots, if positively he 
tropic, will bend their tips, in the course of a few to seve 
hours, directly or obliquely against the stream. Since the rool 
grow against the mechanical pressure of the stream and display 
a latent period and an after-effect, rheotropism is assumed to 
be a response to irritability. The stimulus for this respoms® . 
can do no better at present than to call the flowing wate 
There may be some unwillingness to regard this as the a“ 
stimulus, seeing that the response to such a stimulus is difficu’ 
to interpret as being to the advantage of the plant. 
brings up the general question of the relation of respo” 
stimulus. 
It is quite certain that there is a chain of causal mecha 
between stimulus and the response which the stimulus set 
se to 
nism™ 
s in 
