June 1900.] BOTANICAL SOCIETY OF EDINBURGH 319 



tion takes place in light equally well in the absence of 

 carbon dioxide. 



A number of similar observations have from time to 

 time been made by various authors with regard to the 

 spores of ferns, and the whole subject of the conditions 

 underlying the relations between light and the germination 

 of eryptogamic spores was carefully investigated in 1893 

 by Forest Heald (4), in whose paper full references will 

 be found to the earlier literature. He was able to prove 

 that, under ordinary conditions of temperature and nutri- 

 tion, the spores of ferns do not, as a rule, germinate in 

 darkness or in blue light, although, when the temperature 

 is raised, germination may take place independently of 

 illumination, and his experiments showed that at a tem- 

 perature of 32° C.- germination occurs regularly in 

 darkness within sixteen days. 



He devoted his chief attention, however, to mosses, the 

 spores of which, when supplied with ordinary inorganic 

 food materials, were found to be incapable of germination 

 in darkness or in blue light, while the only effect of raising 

 the temperature to 32° C. was shown in a considerable 

 retardation of germination, which, however, always took 

 place when, at the close of the experiment, the spores were 

 exposed to the influence of normal illumination at ordinary 

 temperatures. A temperature of 35° C, however, proved 

 fatal in four days. When, on the other hand, a small 

 percentage of peptone or glucose, either together or 

 separately, was added to the normal inorganic culture 

 solution employed, germination took place as freely in 

 darkness as in light ; and, in some cases, the growth was 

 even more vigorous in darkness with, than in light without, 

 organic food. 



As in the case of seeds, these spores germinated under 

 the influence of light independently of the presence 

 of carbon dioxide in the atmosphere, showing that the 

 effect of illumination cannot be accounted for along the 

 lines of a photosynthetic formation of carbohydrate sub- 

 stances set up by its action on the chlorophyll always 

 present in ripe moss spores. 



The spores of Marchantia behaved in the same way 

 as those of the higher bryophytes, while, on the other 



