250 BOTANICAL GAZETTE [OCTOBER 
"4 from becoming actual, such as the formation 
e i of wound-cork, excretions, periodic alterations 
y ~ in turgidity, etc. The physiological alterations 
consequent upon the arrangement of two plants 
z, in a xeno-parasitic relation are of a saltatory or 
\ / mutative character, yet no evidence is at hand 
as to the manner in which such alterations 
> become fixed and transmissible. A perfectly 
a, graded series of parasites may be selected 
: which exemplify all stages of dependency, atro- 
phies or reductions, and adjustive arrange- 
ments; but nothing may be assumed as to the 
manner in which progress has been made from 
one stage to another. It 
seems fair to conclude, 
however, that the evolu- 
tionary movement is 
generally toward in- 
creased dependency 
of the parasite, ac- 
companied by ac- 
centuated and more 
complete atrophies. 
The view that such a 
movement may some- 
times ultimately lead 
to extinction, al- 
though by a long and 
indirect way, seems 
also justifiable by in- 
ference, although 
such an end must not 
be assumed for all 
groups of parasites. 
1.—Cissus laciniata parasitic on 
Tse Blakeana; the host has been 
a to expose the roots of the xeno- 
KaxMovtes parasit 
