198 The Beneficial and Injurious Influences of Fungi. 



previous results ; thus the varieties with thick cellulose cell 

 walls were always watery or soapy when cooked and the 

 varieties with thin cell walls were always mealy or floury. 



When a variety is newly raised from seed it has a thick cell 

 wall and is consequently undesirable in the market for its 

 cooking qualities, however desirable it may be for its pro- 

 ductiveness on yielding larger and better shaped tubers. It 

 is then to a great extent resistant to the disease ; after a period 

 of growth, the cell walls become thinner and the tuber more 

 desirable for the table, but often losing its high productivity, 

 and at the same time becoming more susceptible to disease ; 

 hence many of the old varieties are completely discarded on 

 that account, although much esteemed for table purposes. 



It was recently pointed out in the Journal of Agriculture 

 that the enzyme, the function of which is to convert the starch 

 into sugar so as to be directly available for growth, has to a 

 great extent ceased to exist, hence growth or sprouting is 

 checked, and it is now believed that this enzyme existing in 

 considerable quantity in a thick cell-walled tuber is the natural 

 fungicide protecting the plant against the attacks of its pest. 



Eight to twelve years seems to be the period a variety of 

 potato takes to run from infancy to old age, when its vitality 

 is lowered, is then subject to disease, and its productivity 

 much diminished. A fillip may be given to the plant by a 

 change of soil and climate, even as sometimes a change of air 

 and occupation is to ourselves. 



Many troublesome skin diseases such as Ringworm, Barbers' 

 rash, Thrush in infants, etc., are attributable to fungi, in fact 

 all human diseases which are infectious or contagious are 

 caused by micro-organisms which may be regarded as of a 

 fungoid nature. The salmon of our rivers and the gold fish 

 of our ponds often suffer from a destructive parasite (Saprolegnia 

 ferax) which causes the fish to become sick, sluggish and even- 

 tually to die, but broadly speaking, Fungi seem to be more 

 fatal to insects than to the other branches of the animal 

 kingdom. Much loss is caused in some years by the malignant 

 silkworm-disease (Botrytis Bassiana) and beekeeping is becom- 

 ing almost impossible at home in consequence of the scourge 

 known as the Isle of Wight bee disease, which has so far 

 baffled experts to counteract. Some insects seem to have a 

 tendency to favour the attacks of a singular class of parasitic 

 fungi, the mycelium of which permeates the dormant and buried 

 chrysalis, sending out an orange-red fleshy club-shaped stem 

 projecting two or three inches out of the ground and tuberculose 

 with flask-shaped bodies containing spores in asci. This 

 fungus (Cordyceps militaris) is not uncommon in damp woods 

 during the autumn months. It is a debatable point whether 

 the fungus is parasitic or saprophytic, but the stronger weight 



Naturalist , 



