PROPAGATION. 29 



in a quiescent state, always ready to start into action if sub- 

 jected to certain conditions that are absolutely necessary 

 to awaken it into active life. The structure of seeds, par- 

 ticularly in the thickness of their integuments, varies so 

 widely in the different species, that it is necessary to study 

 closely the characteristics of each, and follow a distinct 

 course with the different kinds. For instance, many acorns 

 germinate so readily, that the merest contact with moist- 

 ure is sufficient to start vegetation ; but, on the other hand, 

 the seeds of Holly and others with hard shells, will often 

 lie dormant in the ground for three and four years. 



The embryo in many of the Coni- 

 fers differs from that of most other 

 exogenous plants in having more than 

 two cotyledons, or seed-leaves. While 

 the seedlings of some present only two 

 seed-leaves, in others there will be a 

 whorl of several sometimes as many 

 as fifteen. Fig. 1 shows a young 

 seedling of Norway Spruce just 

 germinating. 



A perfectly ripened seed will retain 

 its vitality just so long as the various 

 substances composing it, such as 

 starch, oils, etc., can be preserved from 

 decomposition. For this reason the 

 seeds of Conifers are generally difficult Fig. 1. GERMINATING 

 to preserve unimpaired for a long 

 time, owing to the excess of oil they contain. Seeds pro- 

 duced by this order should, invariably, if possible* be 

 allowed to remain in the cones until wanted for planting, 

 as no artificial package can supply the place of these 

 natural receptacles. 



Darkness, although not in all cases a necessary condi- 

 tion in the germination of seeds, is, however, important ; 

 as in the absence of light the chemical changes take place 



