668 FORM AND SIZE OF PARTICLES EMPLOYED IN CONSTRUCTION OF PLANTS. 



a fundamental difference between the construction of crystalline bodies and plant 

 bodies; that this very difference is bound up with the distinction between inani- 

 mate and living structures, and that especially are the organized parts of plants 

 fitted by their characteristic structure to those movements which appear to us as 

 life. 



Molecules, united in the growth of crystals, admit of no further insertion of 

 plastic substance, of no rearrangement and transformation, of no addition of new 

 molecules between those already present, as is the case with the molecules of living 

 organized bodies. When the molecules of water penetrate into a salt crystal, the 

 molecules of salt separate from one another, and break away, so that we have a 

 disintegration and solution of the crystal, and not its further development. The 

 crystal, moreover, never shows at any time those displacements and movements 

 of the smallest constructive particles which characterize the living organized 

 parts of plants, which in the aggregate we call life. Crystals, therefore, cannot 

 be considered as organized bodies; they are not directly concerned in the 

 phenomena of life, and form no object susceptible to the influence of that specific 

 natural force which we call vital force. They are not, and will never be living, 

 just as they cannot die. 



The analogy between the structure of crystals and of plants consists only in 

 the fact that in both cases the grouping of the molecules cannot proceed irre- 

 gularly, but must always follow definite laws of symmetry. In both cases the 

 external visible form of the finished structure is the expression of a particular 

 and specific grouping of the molecules, and of molecular aggregates known as 

 tnicellce. 



Many attempts have been made to glean some idea of the actual shape of these 

 groups of molecules or micellae, the bricks — so to speak — of which the plant is 

 constructed. That the hypotheses brought forward are very divergent is not sur- 

 prising when we remember how few are the data of actual fact that have been 

 observed, and how readily these data admit of varying interpretation, and how 

 full a scope they offer to the imagination of the investigator. 



Not long ago the idea found almost general acceptance that micellae were 

 crystalline in form. In many cell-walls, and especially in certain Desmidiese, very 

 regular systems of striae were observed, which ran off into three dimensions of 

 space, and strongly resembled the striae connected with the cleavage planes of 

 certain crystals {e.g. of calc-spar). Since these, and generally all cell-walls, light up 

 the dark field in the polarizing microscope, that is to say, appear doubly refractive, 

 the assumption was supposed warranted that the cell-walls and other organized 

 substances consist of crystalline doubly refractive micellaa, which lie loosely but 

 in regular arrangement next one another. It was imagined that every micella was 

 surrounded, when moist, by an envelope of water, and that on drying, the micellae 

 came into mutual contact. But later researches have shown that the double 

 refraction can be produced by pressure and strain in substances which do not 

 normally exhibit this property, and that the refraction in the polarizing micro- 



