264 RESEARCHES ON FUNGI 



ten days. These fruit-bodies, doubtless, had already shed spores for some 

 time before they were gathered. 



After the number of spores produced had been estimated and the length 

 of the spore-fall period had been observed, it was calculated that large 

 fruit-bodies of Psalliota campestris, Coprinus comatus, Polyporus squamosus, 

 Arc, shed about a million spores a minute for two or more days. 



Chapter IX.— The fruit-bodies of corky or leathery consistency growing 

 on sticks and logs are xerophytic. They can be dried up without any loss 

 of vitality. On access to moisture they revive in a few hours and resume 

 the function of discharging spores. The retention of vitality after desicca- 

 tion in some species is continued for years. The spores liberated from 

 revived fruit-bodies are capable of germination. Typical genera consti- 

 tuting a xerophytic hymenomycetous log-flora are : Lenzites, Polystictus, 

 Stereum, &c. 



The fruit-bodies of ScMzopJiyllum commune possess special adaptations 

 for a xerophytic mode of existence. The gills are partially or completely 

 divided clown their median planes into two vertical plates. Whilst desicca- 

 tion is proceeding, the two plates of each of the longer and deeper gills 

 bend apart and spread themselves over the shorter and shallower gills. 

 "When desiccation is complete, the whole of the hymenium is hidden from 

 external view and the fruit-body is covered both above and below with a 

 layer of hairs. The closing up of the fruit-bodies at the beginning of a 

 period of drought serves to protect the hymenium from external enemies. 

 A fruit-body can retain its vitality in the dried and closed-up condition for 

 two or more years. When allowed to absorb free water through the top 

 of the pileus, it revives in a few hours. The two plates of each pair return 

 to their original vertical positions, and again become closely apposed. The 

 liberation of spores is then recommenced, and may last for some days. 



Chapter X. — The fruit-body in some species can only be developed so 

 as to produce a pileus when subjected to the morphogenic stimulus of light. 

 When a hymenium has once been produced it sheds its spores indepen- 

 dently of light conditions and of the direction of gravitational attraction. 



So long as a fruit-body itself contains sufficient water, spore-discharge 

 appears to continue without being affected by the hygroscopic state of the 

 atmosphere. 



Some of the xerophytic fruit-bodies growing on logs, &c, continue to 

 shed their spores at the freezing-point of water. The range of temperature 

 permitting spore-discharge in the case of Lenzites betulina was found to be 

 approximately 0°-30° C. 



When a fruit-body is placed in hydrogen or carbon dioxide, the libera- 

 tion of spores quickly ceases. The presence of oxygen in the surrounding 

 atmosphere appears to be essential for the continuance of spore-discharge. 



