288 



BOTANICAL GAZETTE 



[OCTOBER 



bry 



from 



examined with the microscope 



in 



men 



tioned. The seeds will not grow normally between filter papers 



or on wet absorbent cotton, prob- 

 ably owing to insufficient water 



supply. 



III. Experiments 



e 



A number of experiments 

 showed that the embryos them- 

 selves have no period of dormancy 

 or need of after-ripening, for fruits 

 just gathered from the plants gave 

 prompt germination when the seed 

 coats were ruptured and the seeds 

 placed in water. Likewise, acid or 

 base-treated seeds never showed as 



Fig. i .—Camera drawing of a longi- high percentage of germination 

 tudinal section of the seed coat of (within 10-30 per cent) as seeds 



Alisma Plantago: a, outer wall of the r t*« ,• ? ,1 A ^ nf 



nut»r i a ™- ~* 11 .• u . fr° m which a portion of the coat 



outer layer of cells, pectic substances ^ 



swelling up and slowly dissolving in was carefully removed. In short, 

 water; b, contents and cross-walls of there is no evidence of stimulation 



the outer layer of cells, largely pectic b the add and b they are 



matenal; c, contents and cross- walls 



of the inner layer of cells, largely slm Pty 



pectic material; d, inner wall of inner for removing an obstruction to 



^ ,° f - ceIls * l[ghtl l suberize d; e, germination, never equaling in 



efficiency the mechanical method. 



Intact seeds that have been 



soaked in water for 12 hours and 



then transferred to 2 mol. sodium 



more or less efficient 



acellular inner layer of coat, possibl> 

 originating from the endosperm, a 

 mixture of pectic substance and 

 hemicellulose. 



shrinkag 



maintain 



These 



determinations are subject to rather large errors owing to the great 

 surface represented by the 400 small seeds used in each test and 

 the error of drying this surface to the same degree before each 



