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were seen to unite into a homogenous layer. Thus he believes 

 to have seen the building of the separate thin lamellae and their 

 subsequent union into a single one. 



The widening-out process has its interest in that it furnishes 

 very strong probable evidence that growth in surface is the result 

 of intussusception. In the first place it is noticed that the walls 

 are but very little thinner here than at other places of the cell, 

 the surface meantime has doubled its original size. Now if this 

 were due to extension alone, the elasticity of the wall must equal 

 IOC per cent., which has not been proven by any experiments on 

 the nature of the cell wall Also to have caused so great an 

 extension, an enormous pressure must be assumed, and this is 

 difficult to account for. The author therefore takes the ground 

 that intussusception must have taken place in producing this 

 growth. He admits, however, that this cannot be considered 

 conclusive proof of this process, but that it furnishes a strong 

 probability to the many already deduced from similar facts. 



The system of stripes in each layer, he holds, consists of spiral 

 bands attached to each other, but originating as a differentation 

 of a layer previously homogeneous, and not, as Dippel and Stras- 

 burger claim, by a local thickening of the membrane. Besides 

 this, he claims to have discovered lamellae running in the opposite 

 direction; these, however, disappear with age, and are supposed 

 to be due to different substances in the cellulose of the membrane. 



At the close the author makes some g-eneral deductions from 

 the facts given, which have already been called in question. (See 

 Botanische Zeitung. June 8, i888.) He says there is another 

 process in the formation of cell membrane quite independent of 

 apposition or intussusception, and names this a new-building. 

 It is doubtful whether this differs from the process generally under- 

 stood by the term apposition. The author, it appears, limits this 

 term to the application of continuous, ready-formed layers to the 

 surfaces of the old walls, while the building of these layers Is held 

 to be something entirely disconnected, and therefore requiring a 

 different name. It is objected to this that as long as we know 

 nothing about the manner of molecular building it is .useless to 

 add another term, and that until we know more definitely about 

 the separate process, the one term, apposition, Is sufficient for both. 



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