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MISSOURI BOTANICAL GARDEN. 



by light may be given by either organic or inorganic solutions. 



Examination of the chlorophyll content of the spores used 

 in the experiments, was made with the result that all of them 

 contained more or less chlorophyll. Alsophila pruinata spores 

 have more chlorophyll than Alsophila australis and germinate 

 much more readily. 



Laage in his work with chemical solutions found that 

 Osmunda spores germinate more readily than other spores, 

 which no doubt is partially due to their having a larger 

 chlorophyll content. 



Some work has been done by Heim and Schulz upon the 

 effect of different parts of the spectrum upon germination, 

 but very little upon the effect of different intensities of white 

 light. 



Effect of Light op Different Intensities upon the Prothallia 

 AND Reproductive Organs. 



First the effects of absence of light will be given. Prothallia 

 of Dicksonia apiifolia that were grown in light favorable for 

 the production of archegonia and which bore them abund- 

 antly, were placed in darkness and left there three months. 

 Although they were covered with water, as were also the cul- 

 tures in light, to insure the freeing of the sperms and the 

 possibility of their reaching the archegonia, no sporophytes 

 developed. Control cultures in light under other similar 

 conditions bore sporophytes in abundance. At the end of 

 the three months the prothallia were paler than when placed 

 in darkness, but still contained abundant chlorophyll. An- 

 theridia developed upon the upper surface near the margins 

 of the prothallia. This production of antheridia in darkness 

 is exceptional and, as far as my experiments were conducted, 

 took place only in mature prothallia that were placed in 

 darkness. 



Spores of Aneimia phyllitidis and Asplenium filix foemina 

 were first germinated in light and when the prothallia, in 

 the two- or four-celled stage, were transferred to darkness, it 

 was found that they had increased some in length, and that 

 the cells were more elongated than when placed in darkness. 

 The extremities of these tubular or filamentous prothallia 



