DISSEMINATION OF SEEDS. 131 



with this debris may be found the spores of Cryptogams 

 and the seeds of Phanerogams which, on reaching a soil 

 adapted to their development, may spring up and flourish. 

 In this way has been explained the abundant growth of 

 certain species of plants on islands far away from the 

 continent on which the species were indigenous. 



Tornadoes, hurricanes, and cyclones often sweep along 

 at the rate of ninety miles per hour and may carry with 

 them heavy fruits and seeds over seas of -considerable 

 width. 



DISSEMINATION CAUSED BY THE ELASTICITY OF THE 

 PERICARP. 



The pericarp of many fruits is possessed of a certain 

 amount of elasticity. This displays itself at the time of 

 the maturity of the seeds by causing the pericarp to open 

 with a sudden spring and thus throwing the seeds with 

 violence and often to a great distance. Many examples of 

 this peculiar property might be named among the most 

 prominent and familiar are the capsules of Echinocystis, 

 Geranium geum, Fraxinella, and Impatiens which dis- 

 charge their seeds with a peculiarly effective jerk. 



The pericarp of Impatiens consists of one cell opening 

 by five valves, and is one of the most common examples. 

 If accidentally touched when ripe, it will immediately 

 burst open ; while the valves, coiling themselves in the 

 form of spirals, spring from the axis, discharge, and 

 scatter the seeds. Hence the common name of one spe- 

 cies, touch-me-not. 



Mr. Thomas Meehan in an article published in the 

 American Naturalist says, " While travelling through a 

 wood recently, I was struck in the face by some seeds of 

 Hamamelis Virginica, the common witch-hazel, with as 



ESSEX INST. BULLETIN, VOL. XIII. 10 



