786 PHYSIOLOGY. 



decay, the seeds should be removed from them. In all cases, 

 seeds when required for preservation should be gathered when 

 quite ripe, as at that period their proximate principles are in a 

 more stable condition than when unripe, when they are very 

 liable to change. Seeds should be also preserved quite dry. 

 Seeds of a farinaceous nature, if ripe and dry, will retain their 

 vitality for a long period, and such may be readily transported 

 to a distance. For the latter purpose they should be placed 

 in perfectly dry papers in a dry coarse bag, which should be 

 afterwards suspended from a nail in a cabin, in which position 

 they are maintained at a moderate temperature and exposed 

 to free ventilation. Such seeds require no further care. But 

 seeds of an oily or mucilaginous nature, or which contain much 

 astringent matter, require, as a further protection, to be excluded 

 from the air. For this purpose they are best packed in stout 

 boxes lined with tin, and filled with dry sand or charcoal 

 powder. The sand or charcoal powder and the seeds should be 

 placed alternately in layers, and the whole firmly pressed to- 

 gether. Such seeds, however, even when thus protected, fre- 

 quently lose their vitality. A coating of wax has in some cases 

 been found to preserve effectually the vitality of seeds. Pro- 

 bably seeds which are difficult of preservation, might be trans- 

 ported in bottles containing carbonic acid, and hermetically 

 sealed. Wardian cases are also an important means for trans- 

 porting seeds (see p. 757), and should be resorted to, when 

 possible, in all doubtful cases. 



Germination. — By germination we mean the power or act by 

 which the latent vitality of the embryo is brought into activity, 

 and it becomes an independent plant capable of supporting itself. 

 The germination of Acotyledonous plants has already been 

 6uffi.ciently alluded to, when treating of the Root, at page 121, 

 and in the sections devoted to the Reproductive Organs of, 

 and Reproduction of Acotyledonous Plants. Our further re- 

 marks will apply therefore solely to Cotyledonous plants. 



Length of Time required for Germination. — The time required 

 for germination varies much according to the nature of the seeds 

 and the conditions under which they are placed. Generally 

 speaking, seeds germinate most rapidly directly after being 

 gathered. If preserved till they are quite dry, in some cases 

 the process of germination is months in being effected. The 

 seeds of the garden cresses will frequently germinate in twenty- 

 four hours, but the majority of seeds do not germinate for from 

 six to twenty days, and some require months or even years. 

 Germination is generally prolonged when the embryo is invested 

 by hardened integuments or albumen ; and it is usually rapid in 

 exalbuminous seeds, more especially if such seeds have thin soft 

 integuments. Heat is the agent which most accelerates germi- 

 nation. 



