26 PLANT DISEASES AND FUNGI. 



" The attacked vines varied somewhat in their appearance, but 

 generally there is a decay of the stem in proximity to the root, and 

 then the whole plant wilts and fails to grow. Sometimes one or 

 more leaves will fall to the ground, and rot away, before the balance 

 of the plant is seemingly affected." 



Dr. Byron Halsted reports® that " a microscopical examination 

 of the decaying stems, leaves, and fruit showed that the decom- 

 posing tissues were teeming 'with bacteria. Inoculations of healthy 

 fruits were made in the usual way, taking the germs from the centre 

 of freshly-decaying cucumbers. It was found that, with no other 

 fungus present, these germs were abundantly able to introduce a 

 rapid decay into cucumbers, melons, and squashes. Cucumbers 

 seem to be the favourite, and in them the decay is the most rapid. 

 It will run from one end to the other, through the succulent centre 

 of a four-inch fruit, in a single day. 



" The next step in the study was the application of these germs 

 to healthy plants in the field. When the inoculation was made near 

 the end of a vine, the latter rotted away in from three to four days, 

 and when nearer the base a longer time was required ; but in all 

 cases an ulcer was formed, which spread more or less rapidly, 

 depending upon the tissue infected. In old stems the decay was almost 

 entirely internal, and did not show much until the disease had spread 

 through the pith to some distant soft parts. A medicine dropper 

 was employed to place a charge in the middle of several petioles of 

 large squash leaves. Upon the next visit, twenty-four hours after, all 

 such leaves had fallen to the ground, and the portion of the petioles 

 below the point of inoculation, six or more inches, in some cases, 

 were thoroughly decayed. In short, the bacterial disease first found 

 in the cucumber, and afterwards propagated from fruit to fruit in 

 the laboratory, as also upon cut stems and petioles, is readily 

 transmitted to vigorous living vines of the cucumber and squash 

 in the field." 



Sixteen seeds of squash were divided, and eight planted in a pot 

 covered with a bell glass, watered with pure water, whilst eight in 

 another pot were watered from the first with the juice of a 

 cucumber which had decayed with bacteria. The first eight seeds 

 germinated quickly, producing large, deep green plants, while in the 

 other pot only two plants appeared above ground, and they were 

 of a dwarfed, sickly-yellow colour, and did not continue to grow. 



8 " Botanical Gazette," Nov.. 1S91. 



