164 
and first comes to destructive action when the latter is sexually mature. 
Here we have a case of u definite periodicity in an infectious disease ” 
explained clearly and naturally by actual peculiarities. The disease 
germs remain latent, and traces even are scarcely to be found. The 
attacked individuals are even stimulated in their growth, and are in 
advance of the sound ones—until suddenly at the time of sexual matu¬ 
rity the disease germs, hitherto concealed within, come into destructive 
operation. 
In smut fungi, which do not live exclusively in the grains, but also 
appear and form smut beds in other parts of the plants, e. in corn 
smut, the infection remains local. The fungous germs proceed to the 
development of smut in the sufficiently young parts of the plants only 
on those spots into which they have penetrated. The plants are recep¬ 
tive to the infection as long as young parts are being produced on 
them. Only when this is no longer the case, i. e., when the plants are 
full grown, does the stage of immunity begin. To what extent the 
peculiarities in the smut fungi and smut diseases, which are now ex¬ 
plained, may be of value for judgment upon similar occurrences in in¬ 
fectious diseases, especially in pathology, is self-evident. 
In conclusion, I may be permitted to observe that seven years 7 labor 
was necessary to reach the conclusions on smut fungi and smut dis¬ 
eases given in my first address four years ago, and in this present one. 
The substance of this address is here made public for the first time as 
original work. 
RIPE ROT OF GRAPES AND APPLES.* 
By E. A. South worth. 
Plate xvi. 
HISTORY OF THE FUNGUS. 
Judging from the bibliography of the fungus of ripe rot and from 
the very scant specimens in the herbarium, it seems to have received 
four or five distinct names at the hands of three or more investigators. 
The fact that it varies greatly in its microscopic and external charac¬ 
ters probably accounts for the vicissitudes of nomenclature through 
which it has passed, and for the fact that one authority has given it two 
and perhaps three names. 
In 1854, M. J. Berkeley described and figured in the Gardeners’ Chron¬ 
icle a disease of the grape caused by a fungus to which he gave the 
name Septoria rufo-maculans. He describes the fungus as attacking 
ripe fruit and causing considerable destruction. From his figures and 
general description there is little doubt that the fungus is the same as 
' * Glceosporium fructigenum , Berk. 
