1923] 



Dormancy in the Seeds of the Persimmon 



85 



Fig. 2. — R'esults obtained after three days under germinating 

 conditions. A, seed intact; B, with outer coat of testa at the 

 micropylar end removed; C, with outer coat and cap removed. 



It is plainly 

 evident that dor- 

 mancy in the 

 seed of persim- 

 mon is due to 

 the structure of 

 the seed coat 

 and not to the 

 embryo, and 

 more specifically 

 to the laj^er of 

 the coat which 



overlies the radicle. But the question is, how does this layer bring 

 about dormancy? Dr. Crocker states that in Iris this cap reduces 

 water absorption by the embryo and this delays germination. In the 

 case of the persimmon, the writer is convinced that while lack of 

 water absorption plays a role in the delay of germination, the princi- 

 pal reason is the mechanical resistance offered by the seed coat to the 

 extension of the radicle. 



There is probably a third factor which is less obvious and more 

 difficult to determine. It is evident that seeds which have been lying 

 in the ground for a year o^* two germinate faster when the cap is re- 

 moved than the seeds collected from fruits. The cause of this differ- 

 ence has not been determined yet, but it is probably due to enzyme 

 production and the increase in power to absorb water. Tests were 

 made for oxidases, peroxidases, and catalases and both fresh and old 

 seeds seem to have an abundance of the last two, while oxidase was no 

 more evident in the older than the fresher seeds. 



How long the seeds lie dormant in their natural habitat has not 

 been determined, but this probably depends upon several factors, 

 such as, location of seed, kind of soil, water relation, weather con- 

 ditions, and microscopical organisms in the soil. Germination seems 

 to take place after the splitting of the testa at the micropylar end and 

 the subsequent weakening of the underlying cap by exposure to the 

 physical and chemical factors of air and soil and to fungal activity. 



Durham, N. C. 



