36 HUMPHREY 
cieze produce spores of similar character. Goebel,' however, 
suggests that localities favorable to Corsznza may not always be 
moist, and in the case of the aquatic Ricciez the perinium very 
effectively serves as a protection against invasion of the spore by 
fungal hyphe. 
Although the great majority of our xerophilous liverworts 
produce thick-walled spores there are such exceptions as Por- 
ella bolanderi and Fradula complanata whose spores are protected 
by a thin, frail exosporium and are incapable of withstanding 
prolonged drying. These liverworts grow on tree trunks or 
exposed surfaces of rocks where they are subject to sudden 
drying out and we should naturally expect their spores to be 
better protected. 
The character of the spore-wall, however, might suggest the 
possibility of these forms being naturally more hygrophilous in 
character, while their adaptation to a dry habitat is merely one 
phase of the extreme adaptability common to both forms. 
In order to get at the relationship of the exospore to the spore 
a study of the life conditions of the several species is necessary 
and some light will be thrown upon the subject when we ascer- 
tain at what time, in nature, the spores of a large variety of 
forms germinate. With a large number of forms it has been 
repeatedly shown that spores sown on soil under conditions as 
nearly normal as possible germinate only after a long period of 
rest. 
In June, 1904, the writer sowed on sterilized earth, a quantity 
of spores of Hossombronza that had been gathered a few days 
before sowing. ‘The culture was made in an earthen saucer 
and placed within another close-fitting earthen saucer, in which 
was maintained a supply of water so that the dirt was kept con- 
stantly moist from below. ‘The culture was placed on a table 
near a window where it could receive a nearly normal supply 
of light. During the latter part of August a few spores had 
germinated but not until October did they germinate in any 
great number. The spore of Hossombronza, while perhaps not 
as well protected as that of Avmbrzarza or Targionza, nevertheless 
is furnished with a resistant exosporium and is well adapted to 
1 Loc. cit., 107. 
