Massee : The Action of Bacterid on Higher Plants. 73. 



a diseased haulm is split open dark brown lines corresponding- 

 to the vascular bundles are seen. These dark lines are due to 

 the vessels beingf crowded with Bacteria, which produce a brown 

 coloration. 



The disease follows the vascular bundles down into the- 

 underground parts of the stem, and thence into the tubers, 

 where it first shows as a pale brown, irregularly broken zone 

 at a little distance from the outside. This coloured zone, which 

 corresponds to the ring of vascular bundles in the potato,, 

 becomes blackish-brown as the Bacteria increase in number, 

 and spreads toward the centre ; finally the potato becomes 

 rotten, and the Bacteria are liberated in the soil, where they 

 remain until another crop of potatoes are planted. 



The leaves or upper portion of the stem are first inoculated, 

 and this is effected by minute beetles and other insects, which 

 feed alternately on diseased and healthy plants. The Bacteria 

 also live in the soil. The most certain preventive is spraying- 

 the crop with Bordeaux mixture to which an insecticide, say 

 Paris green, is added. Lime has a retarding influence on the 

 Bacteria present in the soil. It is also advisable to discontinue- 

 planting potatoes for some time in land that has produced, 

 a diseased crop. 



Hyacinth Bacterial Disease. 



This peculiar disease, so far as is known, is confined to 

 hyacinths. Infection occurs in the leaves or flowers, the germs- 

 being carried by insects. The infected portion is restricted to- 

 the vascular-bundles, the parenchymatous portion of the plant 

 being too acid for the development of the Bacterium. When 

 once infected the disease follows the vascular-bundles of the leaf 

 or flower-stalk into the bulb, its course being marked by clear 

 yellow streaks. Daughter-bulbs produced by an infected bulb 

 are also infected, the disease passing from parent to offspring 

 along the vascular-bundles. Bulbs that are diseased do not 

 produce flowers. 



The Bacteria pass from the diseased plants into the soil, 

 where they are capable of existing for a long time ; hence 

 ground that has produced a diseased crop should in future be 

 avoided for hyacinth culture, unless it has been thoroughly 

 sterilsed by the use of gas-lime or other substance. 



Tomatoes, Swede turnips, and certain conifers are also 

 attacked b}^ Bacteria, and in almost every instance infection 

 is effected by means of insect agency in the first instance. 



1904 March i. 



