350 SCIENCE PROGRESS. 



that the pectose is situated under the internal layer of 

 cellulose. 



Kabsch (14) found that when a cell-membrane is swollen 

 by the action of chlor-zinc-iod, the inner layers only take on 

 the blue coloration of cellulose and that the middle lamella, 

 or so-called intercellular substance, varies in different cases, 

 sometimes remainino- colourless, sometimes appearing yellow 

 and occasionally taking a pale blue tinge. He consequently 

 locates the pectic bodies in the middle layer and says that 

 the inner layers consist only of cellulose. The middle 

 lamella thickens as the cells grow older and the increase of 

 the pectic material is due according to him to transformation 

 of the substance of the primary membrane. 



Vogl(i5), who wrote at about the same time as Kabsch, 

 takes the same view as to the origin of the pectic substances 

 in the wall. His experiments were made chiefly on the 

 roots of Taraxacum officinale and a species of Podospermiim. 

 He found that the innermost part or layer of the cell-mem- 

 brane is composed of cellulose, next to which is found a 

 layer of a mixture of cellulose and pectose, and concluded 

 that the latter was derived from a process of transformation 

 of the older part of the cell-wall. Most externally he 

 identified the so-called intercellular substance, and he says 

 he considers it due to a transformation of the cell-membrane 

 proceeding from without inwards, the resulting material 

 being pectose. V^ogl accounts for the cell-fusions of the 

 laticiferous vessels of those plants by a transformation of the 

 original cellulose septa into a soluble pectose which becomes 

 dissolved. 



W iesner (16) a year later, supporting the conclusions ot 

 Kabsch and VogI, carries them further and applies them to 

 the lignified and corky cells as well as the parenchyma. 

 Working especially on the beet, he describes the fate of all 

 the tissues, saying that all the cells alike begin by being the 

 seat of pectic transformations from cellulose, and that while 

 the cortical membranes remain in different stages of this 

 metamorphosis this is in woody and suberised cells followed 

 by further transformations, leading to the recognition of 

 lignified and corky walls. There have thus been advanced 



