secretary's budget. 84T 



minutes, and then either die or thrust out a slender tube, capable, as 

 in the other form, of becoming a nrature plant inside of the potato 

 plant. All this wonderful vital activity, so readily observed under the 

 microscope, takes place, as we have seen, in bodies small enough to 

 rest easily on the poin of a pin and light enough to be readily blown 

 from field to field. 



The mature fungus lives in the tops or tubers of the potato, and is 

 also a minute affair. Its presence can only be detected by the micro- 

 scopist, but its capacity for mischief bears no relation to its size. It 

 consists of very numerous, colorless, irregularly branching, tube like 

 threads. These threads grow through the tissues of the potato more 

 or less rapidly, appropriating to their own use the nutrient juices of 

 the vegetable, and impoverishing its tissues so that they either break 

 down directly or are invaded by bacteria and other low forms of life 

 which induce putrefective decomposition. It is this mature fungus 

 which sends to the surface the white forests of tiny stalks bearing the 

 summer spores already mentidned. These spores live only a short 

 time, but the mycelium (the internal tube-like threads of the fungus) 

 is perennial and hardy. There is little, if any, differentiation of parts 

 or distinction of function in the internal portions of the fungus, and 

 consequently, unlike the higher plants, a new plant may, under favor- 

 ing conditions, arise from any least portion of it. In fact, any portion 

 of it is a complete plant in itself, being capable of gro'vth and repro- 

 duction. 



There appears to be some hope of successfully combatting this fun- 

 gus more than in the case of almost any other similar plant parasite 

 which is equally widespread. The important facts to be considered in 

 devising preventive measures are (I): The fungus spreads from one 

 plant to another during the growing season by summer spores, rain- 

 washed or windblown ; and (2) it depends, primarily, for its spread 

 the following season upon its perennial mycelium (the tube-like 

 threads), always to be found in the diseased tubers and tops. It may, 

 also, possibly grow from resting spores found in the same situations, 

 although the existence of the latter is not settled beyond dispute. 



PREVENTIVE MEASURES. 



1. From what has been said it follows that the parasite may often 

 live over winter in the tops of decaying tubers left in the fif^ld after 

 harvest. Prudence would, therefore, dictate the complete removal and 

 destruction of such refuse. It should be buried or burned. It should 

 not be used for compost. 



