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I 





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3 

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1907] CROCKER—GERMINA 



377 



were gathered on October i, while yet grcen^ from one of the lagoons 

 of Washington Park. Some of the green seeds were removed from 

 the capsules and placed in distilled water, which was changed twice a 

 day and kept at 23^0. Within a week twenty per cent, had gcr- 

 minated. A portion of the seed stalks were placed in distilled 

 water repeatedly changed and kept at 2 3*^0 . Many of these seeds 

 germinated while yet green and in the capsules. Still other seed 

 stalks were kept in distilled water in an ice-chest at 6^C. None of 

 these seeds germinated, but after three weeks many had ripened, as 

 indicated by the hard brown coats. When the seeds with mature 

 coats were kept at either 23^ or 29° none germinated. Likewise 

 seeds of Poiamogeton natans and P.^ectinaHis, when gathered green 

 and put into distilled water at 23*^ C. which was repeatedly changed, 

 gave a considerable percentage of germination, while seeds allowed 

 to ripen in the cold water of the ponds and then kept at 23° or 29° 



germinate 



Ifth 



germination 



of these seeds are to be determined, the embryos must be freed from 

 any possible effect of the coats by carefully rupturing them ^Adthout 



m 



injuring the embryos. An experiment, the results of which are 

 embodied in the accompanying table, shows conclusively the effect 

 of the coats on germination, as well as the true condition of the 

 embryos as to dormancy. Ripe seeds were used in this experiment- 

 To guard against any possibility of acid formation by fermentation, 

 the seeds of Potamogeton were entirely freed from the fleshy material 

 surrounding the hard seed coat, all were sterilized in five per cent. 



mmu 



distilled water. The coats of one-half the seeds of each species were 



with 



F 



naturally emerge from the coats. This is a very tedious process, 

 because the seeds are so small (especially those of Sagittaria, Typha, 

 and Alisma), and because great care must be taken not to injure the 



.4 erabr^'os. After this treatment the seeds were put into sterilized 



distilled 



During the first two 



darkness 



Within an hour after the coats were broken the cotyledons projected 



account 



In one 



