THE SEED. 



are consolidated or more or less coherent by their contiguous faces 

 into one mass, or are confer ruminate, as in the Horsechestnut (Fig. 

 661). 



639. In the Cuscuta, or Dodder, which never produces foliage, 

 the emhryo is also entirely destitute of seed-leaves or cotyledons 

 (Fig. 122- 124). Here these organs are suppressed in an embryo 

 of considerable size ; but in most such parasites, the embryo is 

 very minute, as well as reduced to the greatest degree of simpli- 

 city, and seems to remain until germination in a very rudimentary 

 state. 



640. On the other hand, the embryo assumes the highest com- 

 plexity in Pines and many other Coniferous plants (400) ; where 

 the cotyledons as they form are increased in number, from two to 

 four, six, or even fifteen, by collateral chorisis (455) ; here the 

 embryo is polycotyledonous. 



SECT. II. GERMINATION. 



641. Our narrow limits prevent us from illustrating the vari- 

 ous arrangements for the natural dissemination of seeds, which 

 would form the subject of an interesting chapter ; and from consid- 

 ering the circumstances under which the embryo retains its vital- 

 ity, in many species ordinarily for a few months only, in some 

 perhaps for many centuries.* We must very briefly notice the 

 conditions under which this latent vitality is called into activity, 

 and the embryo developes into a plant. 



642. The conditions requisite to germination are exposure to 



* It is well known that seeds which have been -kept for sixty years have 

 germinated ; and it seems that grains of wheat, taken from ancient mummies 

 under circumstances which leave little doubt of their high antiquity, have 

 been made to germinate; but in these cases there are several sources of possi- 

 ble deception. Dr. Lindley records the remarkable case of some Raspberries, 

 "raised in the garden of the Horticultural Society from seeds taken from the 

 stomach of a man, whose skeleton was found thirty feet below the surface of 

 the earth, at the bottom of a barrow which was opened near Dorchester. He 

 had been buried with some coins of the Emperor Hadrian; and it is therefore 

 probable that the seeds were sixteen or seventeen hundred years old." Most 

 seeds, when buried deep in the soil, where they are subject to a uniform and 

 moderate temperature, and removed from the influence of the air and light, 

 are in a favorable state for the preservation of vitality, and will germinate 

 when brought to the surface after a long interval. 



