37 
The vitality of the conidia is much greater than I had supposed. In 
one instance roll cultures from dry material a year old gave results, 
although only a portion of the conidia germinated. Spores from other 
samples failed to grow. More tests will have to be made before we 
have anything like an accurate measure of the vitality of the conidia, 
but it is probable that these alone are sufficient to tide the fungus over 
winter. There is, however, no question as to the existence of a resting 
mycelium within the mummified fruits. The sudden general appearance 
of the blight on the Delaware and Chesapeake peninsula this spring is 
a matter of special interest in connection with the fact that there was 
no twig-blight and no rot of the fruit in 1890. There was no fruit which 
could rot, owing to the destruction of the entire crop by spring frosts; 
and being in the orchards much of my time from April to November, I 
did not observe a single blighted twig, although anxious to collect it. 
In the spring of 1891 the blight of the twigs of the peach was a com¬ 
mon occurrence on the upper part of the peninsula, i. e., in five or six 
counties. It attracted general attention and in Sussex Couuty, where 
it was most injurious, it was named 11 the scald,” and was very generally 
ascribed to the heat of the sun. In Maryland it was attributed to frosts. 
Observations in many orchards showed that it appeared immediately 
after rain during the time of flowering, and that it penetrated exclusively 
through the blossoms. Heretofore I had supposed it capable of penetra¬ 
ting through the unbroken cuticle of young shoots, but such cases must 
be exceptional. An examination of hundreds of twigs in all stages of 
blight showed that every one was associated with blighted and persistent 
flowers. In a majority of cases the entire twig was killed, i. e., the 
distal end beyond the point of entrance (Eflate v, Fig. 1). The ex¬ 
tremities of the twigs blighted either under the direct action of the 
mycelium or simply from arrested nutrition due to injuries farther down 
the stem. It was not difficult, however, to find cases (Plate v, Fig. 2) 
where only one blossom and a small portion of the adjacent stem was 
affected, the parts above and below remaining intact. The uniform 
persistence of the blossoms and the size of the twisted, withered leaves 
(Fig. 1) showed very clearly for many days that all the injury was done 
at one time. Some weeks later, under the influence of warm weather, 
many restricted blight spots, as in Fig. 2, took a new growth, girdling 
stems and wilting good-sized green leaves and fruits, but I looked in vain 
for new infections. 
For 3 weeks following blooming the weather was dry and the blight 
was restricted almost wholly to stems of last year’s growth. But I 
found a number of stems in which it had involved the growth of 1889, 
and saw enough to convince me that with wet weather and high tem¬ 
perature such cases would have been as common as in the summer of 
1887, when the fungus entered the stems, by way of the rotting fruits.* 
* This method of penetration was also common in Maryland and Delaware in the 
summer of 1891, and early varieties blighted almost as badly as in 1887. 
