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



of the cell we always see therein granules, rods, and shorter or longer, straight 

 and curved tortuous threads, twisted in balls, and anastomosing into net-works, 

 which undergo the most wonderful displacements, as will be described in the 

 following pages. 



All these observations at any rate do not contradict the supposition of reticular 

 micellae; and since the conception of molecules built up from atoms grouped in 

 this manner has not been contradicted by chemists, the hypothesis should find 

 supi^ort from this fact. Of course the hypothesis of the net-like form of the 

 micellfe is based upon an assumption, the accuracy of which is subject to many 

 doubts. It is questionable whether the same rule always holds in all these 

 groupings and connections. Just as pointed crystals often join up into spherical 

 groups, whose construction follows other laws of symmetry than are observed 

 by the molecules of which the individual crystals are composed, so it is always 

 possible that the combination of the micellse into visible bodies follows other 

 rules than the union of the molecules into the micellae. 



This change in the relations of symmetry, occuring in minerals, gives rise 

 to the idea of the possibility that micellaj may possess a spherical shape, that 

 is to say, the highest degree of symmetry which can be imagined in a body. 

 Some form of symmetry must exist under all conditions, and if the crystalline 

 form of micellfe is excluded, then there remains the possibilitj^ of reticular and 

 spherical micellae. 



Although our thirst for knowledge finds but little satisfaction in hypotheses 

 of this kind, still they are not on this account to be held in contempt. The 

 minutest structure of every substance, whose movements appear to the pei'ception 

 of our senses as life, is far too complicated for us to be able to bi-ing it into the 

 scope of our observations on the life of plants; and in order that we may be 

 able to form a clear picture of all these matters, it is better at any rate to 

 imagine the groups of molecules as net-works and spheres than to imagine nothing 

 at all. 



Though we may deny to the micellffi a crystalline nature, actual crystals can 

 be produced by many organized portions of plants. Groups of crj'stals of calcium 

 oxalate (see fig. 123'') are found verj'- regularly deposited in the net-work which 

 forms the pellicle of myxomycetes. Such gi'oups of crystals are also to be found 

 in the cell-membranes of many flowering plants (Cactacese, Nyctagineaj, Com- 

 melynaceaj, &c.). The carbonate of lime excreted in the cell-walls of Litho- 

 thamniese, is likewise crystalline. In other cases these excretions and depositions 

 of lime and of silica are not crystalline, but amorphous, which literally means 

 without form. But we must be careful not to be misled by this expression. 

 These substances cannot be conceived of without a definite shape governed by con- 

 ditions of symmetry, only they are not composed according to the laws of symmetry 

 governing crystals, ami the word amoi-phous should therefore be interpreted here 

 as non-crystalline. It does not lie within the scope of these remarks to enter 

 into details about the hypotheses as to the shape of the molecules and gi-oups of 



