PICKETT: RESISTANCE OF PROTHALLIA TO DESICCATION 643 
conditions. In the second and third cases full ventilation was 
secured by allowing the jars to rest on blocks of wood 2 cm. high. 
Fourth, large portions of a culture were placed in a desiccator over 
c.p. sulphuric acid and the whole apparatus was kept in a cool, 
moderately lighted location. In all cases, when soil and pro- 
thallia were removed from a dry chamber they were placed in 
contact with moist soil under a bell-jar subject to full diffused 
light at a temperature of 16-20° C., for recovery. Examination 
for dead prothallia was made after three or four days under such 
conditions. Extreme care was taken at all times when removing 
portions of cultures to or from the dry chambers, to leave the 
prothallia as far as possible undisturbed and uninjured. 
Results—glycerin desiccator.—A large portion of the soil of a 
culture was removed to the vial of the desiccator and allowed to 
remain in the dry air undisturbed, except as small portions were 
removed for recovery and growth. Specimens placed in the 
desiccator on March 22 seemed to revive completely up to April 22, 
at which time a few small dead prothallia were found in a portion 
removed. Another portion removed April 29 showed about 50 
per cent of the prothallia dead. The last of the soil and prothallia 
was removed May 5. All the smaller plants and all but a very 
few of the larger plants were dead at that time. 
In this set of experiments a very few fully matured prothallia 
survived continuous exposure to dry air for forty-four days. 
Very few were damaged by such exposure for a period of thirty 
days. That the recovery was complete in case of survival is 
proven by the continued growth of the prothallia and their later 
production of sporophytes. 
That vigorous desiccation follows immediately after the plants 
were placed in the vials is shown by the fact that the soil had 
given up all free moisture in twenty-four hours after being placed 
therein. As a check, at the beginning of this experiment a clump 
of thrifty mature prothallia of Onoclea Struthiopteris was placed 
in one of the vials. After forty-eight hours’ exposure to the dry 
air not one plant recovered. 
A similar set of experiments was arranged with the whole 
apparatus exposed to the direct sunlight. Most of the prothallia 
so exposed were dead at the end of twenty-eight days, and all were 
dead after thirty-five days of exposure. 
