402 DISEASES OF PLANTS. 



The following is the substance of some remarks on the Potato-dis- 

 ease by Dr. Alfred Carpenter : — 



"Eesting-spores of Fungi are very abundant in places where potatoes 

 are usually stored. They do not produce mycelia until the proper 

 juices are ready for their development, and they also require certain 

 physical agencies, such as moisture, heat, and the proper kind of 

 exhalations from damp unventilated ground, with a disturbed state^ 

 of the earth and air. The Tuber is planted with the resting-spore in" 

 the eye. The haulm is sent up with the spore in its tissues. About 

 the time of flowering the juibes in the plant are matured sufficiently 

 for the development of the resting-spore. If at that time we have 

 moisture, undrained ground, and electric disturbance, with luxuriant 

 tops to the plants, the fungus is developed most rapidly. Millions of 

 spores are wafted over the field, and .these are not resting, but developing 

 spores. They send out the mycelia through the stomata, and in a few 

 hours the whole crop is poisoned. Every potato receiving juice 

 from the haulm becomes diseased. These fungus-spores abstract the 

 juice of the plant, and destroy the character of its circulating fluid. 

 Highly manured land and crops make the disease spread more rapidly. 



" We must destroy the germ before planting, by using a pound of 

 quick-lime stirred into a bucket-full of water, with an ounce of carbolic 

 acid of commerce added. ' This quantity will serve for the dressing of 

 a sack of potatoes. 



" Potatoes require to be kept dry ; exposure to the sun helps to 

 preserve them. 



"After the attack of Peronospora infestans, another fungus generally 

 appears, called Fusisporiuin Solani. This acts on the starch, and 

 destroys it ; so that, if you wish to use the starch, it must be done 

 before the appearance of Fusisporium. 



"In preservation from potato-disease three things have to be attended 

 to: — Isi, Choice of seed (tubers). 1i, Removal of mycelia and resting- 

 spores from the seed chosen. Spread seed potatoes out in the sun, and 

 let them dry and become somewhat green. 3d, The preservation of the 

 seed itself Keep it in a temperature to prevent growth of mycelia 

 or the development of the Entophyte, which wUl not grow below 

 48° F. Tubers should be kept in an outhouse where the temperature 

 will not rise above that, nor sink below 35° F." 



In the case of the potato-disease the spores may perhaps follow the 

 same course as that mentioned as occurring in the barley and the wheat 

 fungus. The spores may be produced in one species of plant in the 

 first instance, and then complete their development in another ; the 

 fungus may thus pass part of its life upon some other Tiott than the 

 potato. This process has received the name of Hetercecium (sVfjog, 

 diverse, and o/x/ov, habitation). 



Other diseases in plants owe their origin to insects. Ea/rcookles, 



