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BOTANICAL GAZETTE ' [JULY 



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for years without germination, but if fermentation were set up, 

 the seeds would soon after begin to germinate. He attributed 

 this to the effect of H+ or OH— ions acting as stimuli on the 

 dormant protoplasm. Muller (15) found that the seeds of 

 Eichhornia and Heteranthera germinate only after desiccation. 

 Crocker (i), working on the seeds of various water plants, includ- 

 ing Eichhornia and others reported by Fischer, has shown that 

 the protoplasm is not dormant. He found that the seeds of Eich- 

 hornia, Alisma Plantago, and Sagittaria germinate readily in dis- 

 tilled water if the coats were broken, and concluded that bases and 

 acids here must have their effect upon the seed coats rather than 

 upon the embryos. He also concluded that the effect of the coats 

 in many of the seeds of water plants is mainly to limit the water 

 rather than oxygen supply, since little if any oxygen is needed by 

 them for germination. 



Kinzel (ii) and Heinricher (8) have shown that in many 

 seeds light is necessary for germination. Seeds kept under ordinary 

 germinating conditions for months in darkness failed to germinate, 

 but when placed in light germinate within a few days. Both 

 Kinzel and Heinricher seem to have taken it for granted that 

 the changes induced by the light have to do with the embryo. 

 But even here it is barely possible that light in some way affected 

 the seed coat, rendering it permeable. 



It has long been known that cold has an influence in some way 

 on the germination of various seeds. Many seeds are thought to 

 germinate only after being subjected to freezing and thawing. 

 But as to the exact effect of the cold in bringing about germination 

 there is as yet nothing very definite. 



Pammel and Lummis (17) found that many weed seeds that 

 failed to germinate under ordinary germinating conditions germi- 

 nated more or less readily after freezing. Pammel and King (18) 

 have shown that freezing and thawing not only increase the per- 

 centage of germination in many weed seeds, but that the seeds 

 thus treated in many cases germinate more quickly than those 

 kept dry before planting. Fawcett (4) likewise has shown that 

 freezing and thawing shortens the dormant period of many weed 

 seeds, and that the percentage of germination of seeds exposed to 



