INFECTION THROUGH NECTARIES. 55 
have studied this phase of the subject experimentally. In 1891,Waite sprayed pure cultures 
of Bacillus amylovorus upon pear-flowers and obtained many cases of blossom-blight. 
This was studied in all stages, from the first incipient multiplication of the bacteria in the 
nectar to the destruction of the flower and the passage of the bacteria down the pedicel 
into the stem. By protecting the flowers from the visits of insects by means of mosquito- 
netting, this artificially induced blossom-blight was restricted to certain branches. ‘This 
particular experiment was made in an orchard in Kent County, Maryland, which was 
remarkably free from natural blight and had been for years. In other experiments, not 
in that orchard, Mr. Waite again produced blossom-blight on certain clusters of pear- 
blossoms by infecting the floral nectaries and by allowing the bees to have free access to 
these blossoms he succeeded through their agency in transmitting blight to other flower- 
clusters on the same tree. One of these experiments took place on the grounds of the United 
States Department of Agriculture, an isolated 
tree previously free from blight being used for 
this purpose. Bees were observed to visit the 
infected flowers and, subsequently, flowers 
on other clusters, which flowers afterwards 
blighted. Some of these bees were caught, 
their mouth parts excised, and cultures made 
therefrom by means of poured-plates in Petri 
dishes. Colonies obtained in this way closely 
resembled the pear-blight organism, and inocu- 
lations therefrom produced the disease in sound 
pear-shoots, thus demonstrating beyond dis- 
pute the actual presence of the pear-blight 
organism on the mouth parts of the suspected 
bees. 
Everybody connected with the plant 
pathological work of the U. S. Department of 
Agriculture at that time had knowledge of 
these results. The writer, among others, saw 
all of the experiments described and knows 
that they were well done and that the above 
brief outline can be accepted as an accurate 
statement of what actually took place. 
In 1898 the writer produced Wakker’s yel- 
low disease of hyacinths on two occasions by 
inoctilating through the flowers, but not all of 
the inoculated plants contracted the disease, 
and nothing is known respecting the natural 
occurrence of this disease as a result of nectarial 
infection. ‘The same year a soft white rot of Fig. 9.* 
hyacinths, of the same type as Heinz’s rot, was 
observed by the writer to originate in particular flowers and end in the destruction of the 
plants. It is deemed probable, therefore, that in the field both of these diseases may some- 
times begin in the floral nectaries and be distributed by nectar-sipping insects. The hya- 
cinth gardens of Holland, where these diseases occur naturally, will afford a final answer 
to this question. 
*Fic. 9.—Marginal leaf-infections on cabbage (No. 400) obtained by atomizing on a pure culture of Bacterium 
campestre, shaken up with sterile water. Inoculated Dec. 9, 1904. a, photographed Jan. 6, with transmitted light, 
marginal halation being avoided by a close fitting paper screen which cuts out leaf-serratures. b, contact print made 
Jan. 5 (lights and darks reversed). ‘This is one of the plants that furnished material for the drawings shown in vol. I. 
