VIII BOTANICAL EVIDENCE 387 



the centre of the earth, and in. that direction only. Tlie 

 roots also developed in consequence of their peculiar growth 

 special morphological characters, a cell -structure which is 

 more or less different from that of other parts of plants. All 

 such speciality of structure has certainly arisen simply as a 

 result of the inheritance of acquired characters, and it consti- 

 tutes the type, the "kind" of the plant. Similarly tlie 

 tendrils of climbing plants — structures which owe their 

 origin to the action of external stimuli, to the inheritance 

 of acquired characters — are essential to the definition 

 of their species ; and equally so are the position and 

 colours of the leaves, etc., which are due to the action of 

 light and air. In all such cases special morphological and 

 physiological characters have arisen in consequence of tlie 

 continuous action of stimuli, and the functional activity in 

 definite directions thereby set up in the cells of plants — 

 direct stimulation and functional action cannot here for the 

 most part be separated. In many such cases the direct 

 effects of stimuli and function, and the inheritance of these 

 effects, are so obvious, that it seems to me we must recognise 

 them unless we refuse to recognise cause and effect altogether. 



Must not the water which a desert-plant stores up within 

 itself, in order to keep itself alive in spite of drouglit, have 

 had an indirect and direct influence on its whole internal 

 constitution? And when a seaside -plant like Salicornia 

 herbacea takes so much salt from the sea-water that it has a 

 salt taste, must not this salt have had an influence on its 

 whole cell-structure — an influence which enters into its whole 

 specific character and which is inherited ? Who would sub- 

 stitute for such obvious action of the simplest causes the 

 accidental variation of the germ-plasm and selection ? 



I will not here present the anatomical evidence of my 

 view, since every text-book of botany will supply it. I will 

 only adduce some especially remarkable and cogent fiicts. 



