94 



be seen, that period shows the depression in the curve. Measure- 

 ments were not taken on the young buttons until they were about 

 two days old. A number at this age averaged 1.2 cm. in length. 



The average growth of this fungus is about one half-centimeter 

 per day. Individual plants sometimes grow as much as a centi- 

 meter per day, but this is not common. Compared to other 

 woody forms, a half-centimeter per day is very rapid growth. 

 Most of these are perennial, and the total yearly growth is only 

 a few centimeters at the most. Probably the fastest growing 

 perennial form that we have is the so-called " Polyporus applana- 

 tusy * Yet from measurements taken during the summer, the 

 fastest growth for any individual was 1.5 mm. per day, while the 

 average growth for a number during the month of August, that 

 being the month in which growth is the most rapid, was 0.7 mm. 

 per day. This is only one seventh as fast as that of Polyponis 

 hicidiis. Compared to slower growing forms as Fovics fovicn- 

 tariiis and Fovics piiiicola, the difference must be much greater. 



This extremely rapid growth means a large amount of added 

 tissue each day. The fungus is about one half-centimeter thick 

 at the apex. Taking one that is only twenty-five centimeters in 

 length, we would have added a daily increment of twenty to 

 twent)'-five cubic centimeters. This must mean a very rapid 

 utilization and transport of the food materials by the fungus. 



As the plant approaches maturity, growth gradually ceases 

 and for the last week or ten days it is very slow. External 

 factors seem to be the cause of the maturing of the plant. For 

 the curve last mentioned, plants were used that came to maturity 

 at a length of about fourteen to fifteen centimeters. If plants 

 had been used that matured at twenty-five centimeters, the only 

 difference in the curve would have been the lengthening of 

 the straight part of it until a height of about twenty-three or 

 twenty-four was reached. The plant seems to be able to keep 

 growing at about the same rate as long as conditions are right. 

 But when conditions are not right, as for instance, lack of mois- 

 ture or nourishment, the plant takes on the mature condition. 



* Fames megaloma Lev., or according to Murrill in Bull. Torrey Club 30: 300. 

 1903, Elfvmgia megaloma (Lev.) Murrill. 



