1907] CROCKER— GERMINATION OF WATER-PLANT SEEDS 



319 



Species 



Condition 



OF 



Coats 



Alisma Plantago 





After i Day 



After 3 Days 



ArrEit 10 Days 



Per cent. 



of 

 germ. 



Eichhornia 



Polygonum amphibium.. 

 Potamogeton natans*. . . 

 Potamogeton pectinatus* 



Sagittaria variabilis 



Typha latifolia 



Entire 



Ruptured 



Entire 



Ruptured 



Entire 



Ruptured 



Entire 



Rupturfed 



Entire 



Ruptured 



Entire 



Ruptured 



Entire 



Ruptured 



o 



86 



o 



o 



81 



o 



42 



o 



47 



o 



92 

 o 



85 



Length 



of 



plantlets 

 in mm. 



Percent 



of 



germ. 



Length 



of 



plantlets 



in mm. 



Percent. 



of 



germ. 



2-4 



2-3 



3-5 



2-4 



2-4 



o 



86 

 o 



98 



o 



85 



o 



SI 



o 



53 

 o 



92 



o 



89 



3-7 

 4-7 



4-7 

 5-8 



4-7 



4-7 



4-8 



Size of 

 plantlets 



o 



98 



o 



98 



o 



85 



o 



SI 



o 



S3 

 o 



92 



o 



89 



2 leaves 

 2 leaves 



20-25"^"^ 



I2_j5mm 



2 leaves 



2 leaves 



I I I . 



* The low percentage of germination here is due to many of the seeds having no embrj'os. 



demand answer. How does a period of desiccation bring about the 

 germination of the seeds of Eichhornia as shoAvn by ]\Iuller^ or of 



r 



Potamogeton as shown bv Fischer? What was the role of the 

 bases and acids in Fischer's experiments? My experiments 

 indicate that drying followed by soaking causes a considerable 

 per cent, of the coats of Eichhornia to crack along the flutings, while 

 it causes the rupture of the coats of Potamogeton along two creases 

 that He at the convex side of the embrv^o. Just how the bases and 



acids work has not vet been determined. 



Fischer 



assuming that they arouse the dormant protoplasm is evident, for I 

 have shown that the embryos respond to ordinary germinative con- 

 ditions almost, if not quite, as readily as any embr\^os to be found. 

 The action that causes the germination must evidently be upon the 



That H"^ and OH" ions, 

 as well as many others, may increase somewhat the rate of growth 

 of the naturally rapid-growing embryos, is not at all improbable. 

 The fact that the coats showed no visible change when treated with 

 acids and bases does not indicate that the coats were not radically 

 changed. I have found that the impermeable coats of many of the 



structures surrounding the embryos. 



made 



nucroscope 



absolute alcohol, and yet no chai 



appears. Experiments are being conducted now to determine the 



f 



A. 



