EFFECTS UPON GERMINATION 797 



Like many other seeds and fruits, the achenes of Chloris ciliata 

 gradually aftor-ripen with dry storage, the process being completed 

 in 8 months (21, 23). Non-after-ripened achenes, at the optimum 

 temperature, 33° to 34°C., required light for germination if they were in 

 the hulls (palea and lemma). The germination in light was not complete, 

 but improved as after-ripening progressed. Completely after-ripened 

 achenes in the hulls gave about 16 per cent germination in darkness at the 

 optimum temperature and about 80 per cent in daylight. Partially 

 after-ripened achenes with the hulls removed were also favored by light; 

 about 55 per cent germinated in darkness at the optimum temperature, 

 and 90 per cent in light. Fully after-ripened achenes -v^dth the hulls 

 removed germinated completely both in light and in dark. 



Light favored germination (22, 27) only at temperatures above 

 22°C., was indifferent at or near 22°C., and inhibited germination 

 below this temperature. At 22°C., however, the effect of light was 

 modified by the stage of after-ripening; achenes after-ripened 2 months 

 were favored by light, those after-ripened 5 months were indifferent to 

 light, and those after-ripened 17 months were inhibited by light. 



High light intensities (21) were more favorable to germination 

 of Chloris ciliata than low intensities, but as after-ripening progressed, 

 the lower limit of intensity required for germination dropped, and 

 the duration of any given light intensity necessary to increase germina- 

 tion fell. Illumination of the achenes with the hulls intact for one 

 or more days followed by continuous darkness favored subsequent 

 germination at the optimum temperature. Since the first day's illumina- 

 tion increased germination much more than the second or later day's, 

 increase in germination was not proportional to the amount of light 

 applied. Diffuse light for 1 to 4 hr. increased later germination in 

 darkness 9 to 19 per cent, and direct sunlight for 2 hr. increased germina- 

 tion 36 per cent. 



Achenes with the hulls intact were so sensitive to darkness, especially 

 in the first stages of germination, that Gassner (21) obtained 10 to 

 16 per cent higher germination with daylight if the achenes were put into 

 the germinator in the morning rather than in the evening. Longer 

 periods in a dark germinator with the hulls intact even at temperatures 

 favorable for germination in light made the achenes "dunkelhart," 

 that is, incapable of later germination in light. Subminimal tempera- 

 tures, 6° to 10°C., in dark germinators for 16 days did not make Chloris 

 achenes "dunkelhart" or injure their germinating power in any way. 

 Three to 11 days in a germinator at 0°C. injured the achenes somewhat 

 and the injury increased with time. Gassner beheved this low-tem- 

 perature injury was due to the tropical nature of the plant. "Dunkel- 

 hart" achenes could be forced to prompt germination by application of 

 nitrates, by the use of soil as a substratum (23), or by breaking the fruit 



