104 



GROWTH OF PLANTS 



We have classified coniferous seeds as seeds with non-dormant embryos 

 that are benefited by low-temperature stratification. The main evidence 

 that the embryos are non-dormant is the fact that conifer seeds in general 

 will germinate and produce normal seedlings at 20° C (68° F) or above if 



100^ »/o GERMINATION 



LOBLOLLY PINE 



so DAYS 



Figure 38. The effect of stratification at 5° C (41° F) for one, two, three, and four 

 months on germination of loblolly pine seeds. Broken hne shows the percentage of good 

 seeds as revealed by embryo tests. 



given sufficient time. One will see from the two sets of curves just men- 

 tioned that the time is likely to be rather long — more than 50 days for 

 some species. Flemion in unpublished work has attempted to determine 

 whether conifer embryos show any of the dormancy characteristics such 

 as those already described for rosaceous seeds. Fig. 39 shows, at left, the 

 typical groAHh of an Austrian pine embryo isolated from a seed that had 

 been held in granulated peat three days at room temperature before it 

 was excised and put into soil. At the right is sho^vn a similar embryo 

 taken from a seed after it had been in moist granulated peat at 5° C (41° F) 



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