3S4 Mr Carpenter 07i the Differences of the Laws 



formed tissues with vital properties, evidently belong to the 

 third class ; as do also most of the changes in which the func- 

 tions of relation consist. Setting out with these general views, 

 we shall endeavour to apply them in detail to the analysis of 

 some of the functions ; and as it is obviously advantageous to 

 select for illustration the instances in which these functions 

 present themselves in their simplest form, we shall commence 

 with the study of vegetable life. 



23. The properties of the elementary tissues of plants may 

 be separated into vital and physical, with some degree of de- 

 finiteness ; since these tissues are frequently but little prone to 

 spontaneous decomposition after the loss of their vitality. 

 Hence we are easily able to satisfy ourselves that the proper- 

 ties of elasticity, hygroscopicity, and that peculiar modification 

 of the latter which produces endosviose, are evidently the result 

 of the mechanical arrangement of the particles of the tissues 

 which exhibit them ; since they are not dependent upon vitality 

 for their existence, and may be imitated by artificial combina- 

 tions of inorganic matter.* On the other hand, these tissues 

 are also possessed, in their living state, of properties which, 

 when called into action by stimuli fitted to excite them, main- 

 tain those changes which essentially constitute the life of the 

 plant, and without which the mere physical properties would 

 be inert. 



24. The first and most general of the actions of a vegetable 

 organism consists in the absorption of nutrient materials from 

 without ; this absorption takes place during every period of the 

 life of the plant, from the first appearance of the embryo within 

 the ovule, to the final decay of the structure. Now, there would 

 seem strong reason to believe that the mere act of absoi"ption 

 is due to the physical property already referred to, as the capa- 

 bility of producing endosmose. The succulent extremities of 

 the spongioles in the perfect plant, or the tegumentary mem- 

 brane of the rootless cryptogamia, serve as the medium re- 

 quired for the process ; but it is important to keep in view, 



* Thin latninje of baked pipe-clay are found to be excellent media for the 

 production of endosmose ; and porous limestones possesss a similar property 

 in an inferior degree. — Dutrochet's Menioires, Anatomiques et Physiolo- 

 giques, vol. i. p. 23, &c. 



