204 BOTANICAL GAZETTE [ SEPTEMBER 
results were obtained repeatedly in the laboratory and in the 
greenhouse. : 
Thrips —Another form of spotting, usually accompanied by 
distortion of the young leaves and often of the stems, was found 
to be produced by thrips. These spots can be readily dis- 
tinguished from the work of aphides, being very irregular in 
shape and having mossy outlines. The changes produced in the 
cells of the leaf, however, are apparently the same as those 
brought on by aphides, except that the mesophyll cells are not 
lacerated. Sections and cultures were repeatedly made from 
such spots produced under our control, but no organisms were 
obtained from the mesophyll in any case. — 
Throughout the work it was found that certain varieties of 
carnations were much more subject to the attacks of both aphides 
and thrips than others. Susceptibility was found to depend more 
upon the inherent characteristics of the individual plants than 
upon the variety. In most cases, however, susceptibility to 
attack is the direct result of improper methods of cultivation 
This is only expressing in another way a fact already well rec- 
ognized by carnation growers, namely, that the disease under 
consideration is one which in most cases can be readily con- 
trolled by care in the selection and propagation of stock and 
attention to all the details of cultural conditions. 
Summarizing it may be said that 
1. The disease of carnations characterized by the symptoms 
already described and generally known as “‘bacteriosis”’ is wide 
spread and destructive. 
2. In the earlier stages of the disease neither fungi nor 
bacteria are present, so far as can be determined by the most 
careful microscopic studies and bacteriological investigations. 
3. As the disease advances various organisms appear, but 
their presence is not constant. 
4. Infection experiments with such organisms, carried on 
under rigid bacteriological conditions, resulted negatively in 
every Case. 
5. Adisease having all the characteristic symptoms of “*bac- 
