THE LATENT VITALITY OF SEEDS. 109 



without diminishing its energy. For it to be so, this mass must 

 evidently continually receive new portions of energy, and this 

 can come only either from the surrounding medium or from the 

 reactions that go on in the protoplasm itself. In the former case 

 the agency consists of radiations of different sorts, and is of a 

 purely physico-chemical order; while this can not be in the sec- 

 ond case. In fact, the life of protoplasm is manifested by move- 

 ments which are combined in such a way as to produce an orien- 

 tation of its parts according to certain structural dispositions 

 succeeding one another in a determined order; phenomena to 

 which ordinary physico-chemical actions never give rise. We 

 are therefore necessarily led to suppose the existence of a special 

 class of reactions of which assimilated matters become capable 

 only after their absorption into this special medium, living and 

 pre-existing protoplasm, into which they penetrate. 



Under this relation we might, in a certain way, compare as- 

 similation to what occurs when combustible matter takes fire on 

 being heated in a furnace in which a combustion is already going 

 on, and is kept up by the new matter. So, one might say, it is 

 only after having been previously put into a special condition by 

 their mixture with protoplasm that assimilable substances react 

 among themselves in such a way as to produce a new quantity of 

 living matter. So one may suppose that protoplasm in the condi- 

 tion of latent life, having become inert but retaining the faculty 

 of reviving, resembles those mixtures formed of substances that 

 do not react except under certain conditions of temperature or 

 other influences, and which, so long as those conditions are 

 not fulfilled, continue indefinitely in contact without combining. 

 Such, for example, are explosive mixtures. 



The presence of assimilable matter in protoplasm or within 

 its range is not sufficient for the production of the phenomena of 

 assimilation and orientation. Certain conditions of temperature, 

 moisture, and aeration have to be realized. As long as they are 

 not realized, and if nothing occurs to change the composition or 

 structure of the energides, they will remain inert, while they re- 

 tain the faculty of evolving anew when the circumstances become 

 favorable again. 



Such condition of chemical and vital inertia may probably 

 endure for a long time, possibly indefinitely. This, as it seems to 

 me, is at least the only way of accounting for the preservation 

 of seeds during very many years. Cases are in fact known where 

 seeds have germinated after so prolonged a rest that it is impos- 

 sible to assume that they have lived during the interval even a 

 retarded life. We cite a few examples. M. A. P. de Candolle * 



* Physiologic, p. 621. 



