GERMINATION. 95 



its opening, and the pericarp is sown entire, or in part, with the 

 seed. Most seeds fall upon the surface of the ground, and nature 

 resorts to various means to secure their dispersion : sometimes 

 they are surmounted by a little plume which takes the wind ; at 

 other times they are furnished with wings, so as to be readily 

 carried to a distance ; they are often conveyed to great distances 

 by the currents of rivers or of the sea ; and occasionally their 

 dissemination is effected in a still more singular manner, for it 

 frequently happens that birds eat fruits, the seeds of which they 

 do not digest, but afterwards discharge at some more or less 

 distant place, where they germinate and grow. 



44. The number of seeds produced by most plants is so con 

 siderable that if every seed germinated, the product of some 

 square leagues of land would be equivalent, according to several 

 calculations, to the vegetation of the whole world. For example, 

 160,000 seeds have been counted on a single stalk of tobacco, 

 arid 629,000 on an elm. But this seeming prodigality on nature's 

 part is only a wise precaution against the numerous causes of 

 destruction to which they are exposed. 



OF GERMINATION. 



45. The term germination is applied to the series of pheno- 

 mena that a seed presents, in effecting the development of the 

 embryo it contains. Germination cannot take place except under 

 a concurrence of circumstances dependent on the seed itself and 

 external influences. The seed must be ripe, enclose a complete 

 embryo, and not be too old. There are some seeds that retain 

 the faculty of germinating for a very long time ; wheat and beans 

 enjoy this property for sixty and even a hundred years, while 

 coffee, on the contrary, loses it in a very short time. Some, when 

 protected from contact with the air, preserve their germinative 

 faculty for a long period : on the other hand, the seed must be 

 subject to the action of certain external agents, the chief of which 

 are water, heat, and air. Water is indispensable to germination ; 

 it acts by penetrating the substance of the seed, by softening its 

 envelopes, by causing the embryo to swell, and by bringing about 

 in the endosperm or in the coty'ledons, chemical changes, which 

 render the substances deposited in their paren'chyma (from the 

 Greek, paregchuein, to strain through, the spongy and cellular 

 tissue of organized bodies) fit to nourish the young plant. Heat 

 is also necessary : below a certain temperature the seed remains 



4<J. Are the seeds of plants very numerous ? 



45. What is meant by germination ? What circumstances are essential 

 to germination ? 



