DISEASES OF GINSENG. 81 



leaf stems into the leaf and carry the water and mineral substances 

 from the soil to the leaves, where they are used in the manufac- 

 ture of plant foods. These tubes are arranged in a circle just un- 

 der the bark of the roots and are the parts of the root affected by 

 this fungus disease. The tuljes are thick walled and there is con- 

 tinually passing up through them a steady stream of water so that 

 as water is lost by evaporation in the leaves more is immediately 

 supplied and thus the leaf is kept rigid and plump, or turgid, as 

 the botanist calls it. Any cause which interferes with the supply 

 of water to the leaves results in wilting or the loss of such an 

 amount of water as is required to keep the leaf plump and turgid. 

 If the supply is cut off altogether, of course the top wilts and dries 

 up completely. If we examine these diseased sap tubes carefully 

 under the microscope, we will find them to contain masses of little 

 fine threads (Fig. 31). These small interwoven threads are the roots 

 of another very small plant, a Junius called Acrostalaimus 

 panax. The small fungus plant is living here because it can find 

 an easy living, "sponging" off the ginseng root. The fact that 

 the walls of the tubes are brown (Fig. 32) instead of white as 

 they should be is a sign that the fungus is disintegrating them 

 and prol^ably using the material of which they are made, for food. 

 The trouljle from this parasitic fungus apparently comes, partly, 

 from the fact that the dense growth of thi-eads of the mycelium, 

 as it is called, chokes up the tul:ies. This prevents the necessary 

 supply of water from passing up to the leaves and consequently 

 the tops wilt and die for want of water, even in a moist soil. 

 Perhaps the greatest cause of the diseased condition is that the 

 fungus produces poisonous excretions which are injurious to the 

 surrounding tissues. This also has its effect on the rise of water 

 through the tubes. 



The fungus has never been shown to enter and infect the 



