128 RIPENING AND DIFFUSION OF SEEDS. 



The greater number of plants ripen their seeds 

 within a year after fecundation; but firs and pine 

 trees require more, and the cedar takes no less than 

 twenty-seven months to mature its cones. 



As soon as the fruit becomes perfectly ripe, the 

 different parts of the seed organ separate in various 

 manners, and the seeds are loosened and scattered by 

 the means which Providence has contrived for con- 

 tinuing and disseminating the species, as well as by 

 the enormous number of seeds produced. Ray counted 

 no less than 32,000 seeds on one poppy plant, and 

 360,000 on a plant of tobacco ; but were all these to 

 be disseminated and grow, a single species would soon 

 overrun the whole surface of the globe, a circumstance 

 prevented by the over produce being eaten by various 

 animals, for whose subsistence, indeed, it seems to 

 have been expressly provided. Animals, indeed, and 

 man himself, are active agents in the diffusion of 

 seeds ; the missel thrush disseminating the misseltoe 

 berries, and the European weeds having become com- 

 mon in America by being carried thither (not inten- 

 tionally) by European settlers. Rivers and seas also 

 diffuse seeds by conveying them to distant regions; 

 and thus islands which rise from the sea by volcanic or 

 other agency, become in time covered with vegetation. 

 The seed-organ itself often opens with a spring-like 

 mechanism, calculated to project the ripe seeds to a 

 distance, as in the balsam, the sand box tree, the wood 

 sorrel, and in the violets. In the latter, as I have 

 observed, the seeds are contained in an organ of three 

 valves, the sides of each of which shrinking and col- 



