21 



For those oxporinionts youti<( rooted cuttinj^s of the Scott, McGowan, 

 and (xarfield earnatioiis. as free as possi))le from i\w disease, were 

 ol)tained. o<» of eaeh \'ariety being set out in a small house, in which 

 the conditions coidd l)e easily controlled, and 50 each in a larger 

 house. In addition to these, seedlings of as many of the species and 

 varieties of Dianthus as could be obtained were also grown, one lot 

 in the small and the other lot in the larger house. The plants in the 

 small house were fumigated with hydrocyanic acid gas and tobacco, 

 and were carefully examined once a week to see that they were per- 

 fectly free from aphides, thrips, and red spiders, while on the other 

 hand the corresponding lots of plants in the larger house were col- 

 onized with aphides and thrips. 



All the young growth that developed in the small house during two 

 months remained free from the disease, although the house was con- 

 stantly shaded and halt of each lot of the plants were syringed each day 

 overhead^ — a treatment supposed to favor the development of the disease. 

 It w'as found that those which were syringed were, on the whole, a little 

 better developed than those left dry. but otherwise there was no differ- 

 ence. In the larger house, however, a marked differiMice was apparent 

 at the end of this period between the two sets of plants, those which 

 had been s^^ringed overhead showing 50 per cent less spot than those 

 kept dry. This difference is readily explained by tht^ fact that the 

 syringing prevented the excessive multiplication of aphides and the 

 increase of red spiders, and also drove off many of the thrips. Had 

 bacteria had anything to do with the disease the plants syringed over- 

 head should have suffered most. Not only did the carnations become 

 spotted from the punctures of aphides, thrips, and spiders, but all the 

 varieties of Dianthus reacted in a similar manner. The thick-leaved 

 forms developed spots much like those on the carnation, while on the 

 thin-leaved forms the spots dried out more (juickly, and the leaves 

 showed greater distortion when attacked by thrips. 



BACTERIA I. INOCULATIONS. 



At the close of the experiments above described the plants in the 

 small house, having an abundant new growth and being absolutely free 

 from insects and mites, were in prime condition for bacterial inocula- 

 tion experiments. Bacterimn dianthl from a fresh, rapidly growing 

 liquid culture was therefore inocidated into ten plants of each of the 

 three varieties of carnations mentioned; three plants each of Dianthus 

 arenarius^ I), chinensis (two varieties), D. cae8iw<^ I), har'hatus^ and 

 D. plumarUiJi^ and sixteen horticultural varieties of these species; and 

 five varieties of seedling carnations — a total of 6 species and 26 

 varieties, including the three varieties first named (111 plants in all). 

 All the young growth, including manj^ of the mature leaves, was 

 thoroughly washed with water and beef-broth solutions containing 

 the germs. 



