Vol. 6 No. 8 



TORREYA •^'B- 



August, 1906 BOTANJCAJ 



THE RATE OF GROWTH OF PANAEOLUS 

 RETIRUGIS * 



By Gertrude E. Douglas 



During the last of March, 1906, mycelium of Panaeohis reti- 

 nigis, scattered throughout the pots in the palmhouse of the 

 conservatory in connection with the Department of Botany of 

 Cornell University, began to put forth fruiting bodies in great 

 numbers. As the rate of growth of mushrooms is a matter of 

 some interest, individuals of this species were selected in as early 

 stages as possible and measured twice a day until they had 

 reached maturity. These measurements were taken in the morn- 

 ing and evening at the same time every day, the day interval 

 between them being of eight hours and the night of sixteen. A 

 large number of individuals were measured during the period 

 from March 22 to April 4, but complete records were obtained 

 from only eighteen, owing to the sensitiveness of the mushrooms. 

 A few of them fell over under their own weight, while others 

 were injured by some disturbance of the soil around them. 

 Although great care was taken in using the dividers, some plants, 

 especially in their early stages, were injured by accidentally touch- 

 ing them with the instruments. 



The first appearance of the mushrooms above the surface of 

 the soil was a small dark-brown button, from 2 to 3 mm. high and 

 2 mm. wide. This developed rapidly. The stem grew very fast: 

 at first and pushed the pileus up into the air. The pileus at the: 

 same time grew rather slowly but steadily, enlarging at about 

 the same rate in all dimensions, the length remaining shghtly 

 greater than the width. Just before the stem had ceased its 



* Contribution No. I13 from the Department of Botany of Cornell University. 

 [No. 7, Vol. 6, of ToRREYA, comprising pages 133-156, was issued July 25, 

 1906.] 



157 



