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MISSOURI BOTANICAL GARDEN. 



vcloped abundantly over almost the entire under surface of 

 the prothallia. 



Prothallia of A. pruimta germinated and grown in light of 

 an intensity of 0.3 had abundant archegonia but noantheridia. 

 About 25 of these prothallia were sectioned and no antheridia 

 were found upon any of them. Later on this culture was 

 transferred to weaker light and antheridia developed. Some 

 of these prothallia took such a position with reference to the 

 light that they were about equally illuminated on both sides, 

 with the result that archegonia were produced on both sides. 



A noticeable effect of different intensities of light upon the 

 form of the prothallium was observed especially in Alsophila 

 pruinata. In very diffuse light of 0.002 intensity the growth 

 was a somewhat branched filamentous form. In stronger 

 light of 0.008 intensity, the prothaUia grew out into ribbon- 

 like forms and bore only antheridia. In these no trace of a 

 meristematic cushion upon which archegonia develop, was to 

 be found. In still stronger light the expanded heart-shaped 

 prothallium was produced which bore both archegonia and 

 antheridia. In more intense light of 0.3 intensity, archegonia 

 but no antheridia were produced upon heart-shaped pro- 

 thallia shorter than those in weaker light. 



Cultures of D. apiifolia, Asplenium filix foemina, and 

 Aneimia phyllitidis produced both archegonia and antheridia 

 when grown in light varying from 0.03 to 0.3 intensity. 



Cultures of Aneimvm phyllitidis and Gymnogramme calo- 

 melanos Mertensii were exposed to light from one side only 



2. GROWTH OP GYMNOGRAMME GERM-TUBE WITH LIGHT 

 ONE SIDE, AND THEN SHIFTED ABOUT 90°, X 100. 



in Petri dishes containing 0.5% Knop's solution. Both of 

 the cultures produced tubular prothallia that were positively 



