CONDITION OF AGGREGATION OF ORGANISED STRUCTURES. ySt; 



polarised Vv^hi in cell- walls, starch-grains, and crystalloids \ They inferred from these 

 facts a crystalline structure of the individual molecules, and that the crystals are 

 doubly refractive, and have two optic axes which are so arranged, at least in the 

 greater number, that one axis of elasticity of the ether within each molecule of the 

 starch-grains and cell-walls is placed radially, but the two other axes of elasticity 

 tangentially. In crystalloids the molecules are probably arranged as in true crystals, 

 but separated also by layers of water parallel to the faces or lines of cleavage. 



The behaviour of grains of chlorophyll and of colourless protoplasm towards 

 polarised light, as well as under the addition and removal of water, is at present but 

 little known ; and a more definite idea of the form of their molecules is therefore not 

 yet possible. 



The solid molecules of one and the same organised body which are separated 

 by aqueous envelopes always vary in their chemical nature ; so that at every visible 

 point molecules which possess chemically different properties lie by the side of and 

 among one another separated by layers of water. In starch-grains, cell-walls, and 

 crystalloids this fact is inferred from the circumstance that certain substances are 

 extracted by the application of certain solvents, while other substances remain behind, 

 constituting what is called the skeleton. This skeleton is of course less dense than 

 the original substance ; and it is evident that the extraction has taken place at all 

 visible points, without the external form or internal structure having undergone any 

 essential change. Thus, for example, a skeleton of cellulose remains behind when 

 the lignin has been extracted from wood-fibres by Schultz's maceration ; and 

 again, a skeleton of silica remains behind with all the optical properties of the 

 cell-wall when the organic substance has been burnt away. In the same manner a 

 grain of starch leaves behind a skeleton containing very little solid material when 

 the granulose has been extracted by saliva or some other substance. From crystal- 

 loids also a skele in this sense of the term containing very httle solid matter can 

 be obtained by the solution of a part of their substance, especially of the colour- 

 ing material contained in them. The properties of these skeletons show that the 

 molecules which remain behind after solution of the rest still occupy essentially the 

 same position and are endowed with the same forces as before ; but it is probable 

 that the extracted substance lay previously between these molecules without being 

 contained in them. This view is also more or less probable in the case of chloro- 

 phyll-grains and protoplasm ; in the former the fundamental protoplasmic substance 

 remains behind as a very solid skeleton when the green colouring material is ex- 

 tracted by ether, alcohol, oil, &c. Very different substances are certainly combined 

 in the protoplasm ; and when a naked primordial cell secretes a cell-wall, it may be 

 assumed that the molecules which form the cell-wall were previously di4ributed 

 between those of the protoplasm, and only change their position and their chemical 

 nature when they are secreted m the formation of the cell-wall ; the protoplasm 

 which remains behind retaining essentially its original properties. The same is the 

 case when grains of starch or chlorophyll are formed in the protoplasm. A funda- 

 mental substance is clearly present in the protoplasm which always retains the 



» Hofmeister (Handbuch der phys. Bot. vol. I, p. 348) h^^ arrived at altogether different con- 

 cUisions, with which I cannot agree. 



