DORMANCY IN SEEDS 107 



Flemion '^ reports that one investigator was unable to obtain any ger- 

 mination of snowberry (Symphoricarpos racemosus) seeds, while another 

 investigator obtained only 50 per cent after two years in the soil. Flemion 

 was successful in getting nearly complete germination of these seeds A\'ithin 

 a year. She summarizes her results as follows: ^^' p-^"' 



"In order to induce germination in seeds of Symphoricarpos racemosus 

 it is necessary that the seed coat be disintegrated. This can be accom- 

 plished by placing the seeds for a period of three or four months in moist 

 acid peat moss at 25° C, or by soaking the seeds in concentrated H2SO4 

 for 75 minutes, or by H2SO4 treatment and several weeks at 25° C. After 

 the required changes in the seed coat have occurred it is still necessary to 

 after-ripen the embryo, which can be brought about by a period of six 

 months at 5° C. Of these three methods which modify the seed coats, 

 the combination of H2SO4 treatment and a short period at 25° C is the 

 best, and germination percentages of 60 to 90 may be obtained in this 

 way. 



"For the production of seedlings on a large scale the best method is to 

 plant the seeds in flats in spring and place out-of-doors in a cold frame 

 which is covered with a board cover during the winter months. Germina- 

 tion occurs the following spring. In nature, as in our laboratory experi- 

 ments, the seeds respond to a high temperature followed by low tempera- 

 ture. During the period at high temperature (summer months) conditions 

 are favorable for the modification of the seed coats; the embryos are then 

 after-ripened during the subsequent cold winter months. 



"That the seed coats undergo changes during dry storage at room tem- 

 perature is sho^^'n by the fact that a suboptimal treatment of sulphuric 

 acid followed by low temperature produced a maximum germination from 

 seeds which had been stored about three months. Practically no seeds 

 stored nine months or longer germinated although they were shown to be 

 still viable when subjected to a more effective treatment. 



"The seeds increased several-fold in catalase and peroxidase activity 

 during the period of after-ripening at 5° C. WTien at 25° C the activity 

 of these enzymes does not increase, but there is instead a slight decrease." 



Pfeiffer ^' made a study of the building up of the seed coat during the 

 development and maturing of the seed, as well as of decomposition of the 

 coat in the soil. Fig. 40 shows the general structure of the seed and coats. 

 The outer longitudinal, many-celled layer of fibers, as well as the circum- 

 ferential inner and somewhat thinner layer of fibers are derived from the 

 ovary wall. Both consist of long, thick- walled cells with small lumina and 

 give the coat its marked leathery toughness. Pfeiffer summarizes her 

 work in part as follows: ^^- p-^-^ 



" The components of the fiber walls and the integument epidermis include 

 cellulose, pentosans, and lignin. Deposition of the substances is in this 

 sequence; the greater deposit of lignin is in the integument epidermis. 



"These wall substances become subject to decomposition by fungi from 



