Pulp Fibers and Paper 



287 



this fibrillation originated from the middle secondary 

 wall of the tracheid. It is evident too from this micro- 

 graph that repeated replication from the methacry- 

 late cast is possible without perceptible loss of resolu- 

 tion, for the carbon replica shown was deposited on 

 the fifr/i PVA replica to be taken from it. 



When the method is applied to rough surfaces 

 in general, the procedure is exactly the same as that 

 described for fibres. Fig. 4 shows the application of 

 the method to the study of wood tissue. The wood — 

 Scots pine — was cut in a radial plane with a very 

 sharp chisel prior to replication. Parts of three cells 

 are seen, the boundaries between which are apparent. 

 The micrograph shows the way in which the layers 

 of the cell wall around the bordered pits have been 

 torn away by this rather crude cutting process expos- 

 ing the underlying layers. Wholly intact replicas of 

 surfaces of paper and of metal fractures have been 

 obtained by this method but space does not permit 

 the publication of the results here. 



Carbon replicas prepared in this way can be ex- 

 amined with advantage by stereomicroscopy. There 

 is always a tendency for the carbon replica of a 

 rough surface to be pulled flat by surface tension 

 forces during the final flow-wash with chloroform. 



However, replicas 70-100 A thick appear to retain 

 approximately their overall form provided that height 

 variations in them are no greater than 5 microns. 

 (For height variations greater than this the replica 

 collapses to some extent but without disrupting.) 

 Stereomicrographs then are capable of yielding in- 

 formation on both the overall form and detailed 

 structure of the surfaces. 



To conclude, this method has been of value in the 

 investigation of the structures of pulp fibres, wood 

 and paper. It could be used with advantage for the 

 reliable replication of large selected areas of rough 

 surfaces in general. 



References 



1. Agar, A. W. (1957, in press). 



2. Dlugosz, J., These Proceedings, page 283. 



3. Emerton, H. W., Page, D. H., and Watts, J., These 



Proceedings, page 287. 



4. Heidenreich, R. D., Rev. Sci. Instnim. 23, 583-594 (1952). 



5. Page, D. H., Research (Loiul.) 9 S, 10 11 (1956). 



6. Ramanathan, N., SiKORSKi, J., and Woods, H. J., 



Biochim. Biophys. Acta 18, 323-340 (1955). 



7. Takahashi, N. and Asaeda, T., Bull. hist, textile Fiance 



35, 75-82 (1952). 



Further Reflection Electron Microscopy of Pulp Fibres and Paper 



H. W. Emerton, D. H. Page, and J. Watts 



British Paper and Board Industry Research Association, St. Winifred's Laboratories, Kenlcy, Surrey 



roLLOwiNG the revival of interest in the reflection 

 electron microscope in the early years of this decade. 

 Chapman and Menter (3) used it in the study of 

 fibre surfaces. Shortly afterwards Emerton (4) at 

 this laboratory proposed its use as a contribution 

 to the study of the effect on pulp fibres of the paper- 

 making process known as beating. The early work in 

 this field has been reported by Amboss, Emerton & 

 Watts (1). It will be recalled from this latter paper 

 that the reflection electron microscope as used for 

 the study of pulp fibres suffers from two main 

 disadvantages. Firstly the specimen is viewed at 

 glancing incidence giving rise to a severely foreshort- 

 ened image. Secondly under the impact of the elec- 

 tron beam the fibre tends to decompose into gases 

 which cause distension of the cell walls. This "bubble 

 artefact" tended to mask the true structure of the 

 fibre surface and was an undesirable feature of most 

 of the early reflection electron microscopy of pulp 

 fibres, in spite of all efforts to keep the beam inten- 

 sity low during examination. It was in an attempt 

 to overcome this difficulty for biological specimens 

 in general that Bradley (2) devised a method of 

 producing solid metal replicas of specimens. Such 

 replicas will withstand high beam intensities without 



damage. The present paper describes our experience 

 of the application of this technique to the study of 

 pulp fibres and paper. 



Apart from the initial preparation of the fibres our 

 technique follows basically that described by Bradley. 

 The fibres are dried down from an aqueous suspen- 

 sion onto a glass slide and replicated in thick plastic 

 from which the robust metal replica is made. Figs. I 

 and 2 illustrate the application of the technique to 

 spruce tracheids that have undergone a fairly heavy 

 beating treatment. Both these micrographs, but more 

 particularly tig. I. which is a micrographic montage, 

 have been reduced far below their useful magnifica- 

 tion to be accommodated on the page. The striking 

 three-dimensional appearance given by the reflection 

 method is vividly brought out. It is this three- 

 dimensional aspect, arising from the great depth of 

 field, the oblique viewpoint and the shadows pro- 

 duced, that permits the form of the fibre surface to 

 be inferred. Both tracheids have been subjected to 

 strong surface tension forces while they were dried 

 to equilibrium with room humidity and this has led 

 to the collapse of the lumen and an almost complete 

 flattening of the cell. This effect, which is common 

 in fibres of this type (i.e. spruce sulphite tracheids). 



