BOTANICAL GAZETTE. 173 



Prof. Strasburger entirely dissents from Naegeh's micellar 

 hypothesis. This hypothesis was based upon the phenomena of 

 "swelling up" which are so characteristic of organized bodies, and 

 upon the optical properties which certain of these bodies possess. 

 Prof. Strasburger points out that swelling up may be as well as- 

 cribed to the taking up of water between the molecules oi the 

 body as to its being taken up between Naeejeli's micellae. He 

 shows also that the double refraction of organized bodies, such as 

 cell-walls, and starch grains, depends upon their organization as a 

 whole; for when once their organization is destroyed, their double 

 refraction is lost, a result which cannot be explained on the micel- 

 lar theory, since the particles of the disintegrated micellae would, 

 like particles of broken crystals, still retain their power of double 

 refraction. . , 



According to Strasburger the molecules of an organized body 

 are not aggregated into micellae which are held together by at- 

 traction, but are linked together, probably by means of multiva- 

 lent atoms, by chemical affinity, in a reticulate manner. Swelling 

 up is then the expression of the taking up of water into the 

 meshes of the molecular reticulum, where it is retained by the in- 

 termolecular capillarity. The more extensible the reticulum, that 

 is, the more mobile the groups of molecules within their position 

 of equilibrium, the greater the amount of swelling up. The limit 

 is reached when the chemical affinity of the molecules and the 

 force of the intermolecular capillarity are equal ; if the latter ex- 

 ceed the former at any moment, the result is the destruction of the 

 molecular reticulum, or, in other words, of the organization. Pro- 

 toplasm differs from other organized bodies in that the grouping of 

 its molecules is undergoing perpetual change, the result of this 

 molecular activity being the phenomena which we term vital. The 

 growth in thickness of cell- walls and starch grains takes place, ac- 

 cording to Prof. Strasburger, by the deposition of successive lay- 

 ers ; in opposition to Naegeli's view, that the mode of growth 

 was intussasceptive, with subsequent differentiation of layers. 

 Even the surface growth of cell-walls is not, in his opinion, intus- 

 susceptive, but is merely due to stretching. 



With reference to the mode of formation of the cell-wall and 

 of the thickening layers, Strasburger agrees with the view of 

 Schmitz that the cell- wall is formed by the actual conversion of a 

 layer of the protoplasm, that is, chemically speaking, by the pro- 

 duction of a layer of cellulose from a layer of proteid. When a 

 mass of protoplasm is about to clothe itself with a membrane, the 

 peripheral layer becomes densely filled with minute proteid 

 bodies, the microsomata, and this layer then becomes converted in- 

 to cellulose. The wall of a young wood-cell of Pinus, for in- 

 stance, is clothed internally with a layer of protoplasm filled with 

 microsomata, which are arranged in spiral rows ; the microsomata 

 then gradually disappear and the layer of protoplasm is found to 



