1886. ] BOTANICAL GAZETTE. 241 
lata is the wecidium of G. clavarieeforme, Rathay maintains that it 
is a form o 
tained both R. lacerata and R. penicillata from sowing the spores 
views of those who are opposed to Oersted’s conclusion. n 
other words, the undoubted Gymn. clavarizforme on J. communis 
country is only a form of Gym. clavarieforme which grows on 
J. Virginiana. This is the view of Schroeter, but it is difficult 
produce on the former what we 
and on the latter what we call 
The Theory of Immunity from Contagious Diseases.* 
D. E. SALMON. 
dual acquires from the effects 
h one attack of the disease 
letely and satisfactorily ex- 
The immunity which an indivi 
of a contagion, by passing throug 
Which it causes, has never been comp 
# Read before the A. A. A. S., Buffalo meeting, 1886. 
