DORMANCY IN SEEDS 



111 



can be reduced to less than six months. In this way the more resistant 

 Crataegus seeds can be made to germinate the first spring after maturity. 

 In the case of less resistant seeds Flemion says: •*^' ^■*" "Although seeds 

 of C. amoldiana, C. carrierei, C. mollis, C. sanguinea, and C. tomentosa 

 germinate after a period at low temperature, more seedlings are obtained 

 when the seeds have been treated in a moist medium for several weeks at 

 21° or 25° C prior to the low-temperature treatment." 



Figure 42. Seedling production of various Crataegus species. Lots of 500 seeds each 

 were planted on Xov. 26, 1932, in flats and kept for various periods at 5° C (41"" F) with 

 and without a previous four months at 21° C (70° F). Photographed six weeks after being 

 transferred to a warm greenhouse. 



Cotoneaster seeds "' behave much as do Crataegus; C. Dielsiana and 

 C. Zabelii show 100 per cent germination within four months when kept 

 in a germinator at 10° C (50° F), while C. acutifolia, C. apiculata, C. hori- 

 zontalis, C. lucida, and C. divaricata show very little germination in this 

 condition even after ten months. These five all respond, as do the more 

 resistant species of Crataegus seeds, to a period in soil at high temperatures 

 for overcoming coat resistance, followed by a period at low temperature 

 to after-ripen the embryos. Like\\'ise the high temperature can be par- 

 tially or entirely eliminated by proper treatment with concentrated sul- 

 furic acid. 



Table 13 shows the data on the seeds described above and a number of 

 other seeds ^- °*- ^® belonging to this class that have been studied at the 

 Institute. It gives the best temperatures for the high-temperature period, 

 as well as the low-temperature period that follows; the range of effective 

 temperatures for each treatment; the number of days required for each 



