306 SUMMARY OF CURRENT RESEARCHES RELATING TO 



minutes in a mixture of 1 ccm. of a saturated alcoholic solution of eosin 

 and 49 ccm. of 97 per cent, spirit. 



Sections by the first method show the connective-tissue fibres stained 

 bright blue, nuclei blackish, all other elements greenish-yellow. In the 

 second method the yellow colour is replaced by red. 



Clearing and Staining of Vegetable Preparations.* — In his 

 researches on the development of Vascular Cryptogams,! Dr. D. H. 

 Campbell strongly recommends the practice of imbedding, and cutting 

 with the microtome for similar investigations. In examining the 

 structure of the megaspores of Pilularia, the spores were imbedded in 

 parafiin, and then cut with a Cambridge rocking microtome. Schonland's 

 methods, with some simplifications, were used in most cases, but in 

 others the spores were gradually brought into clove-oil, and then into 

 xylol instead of turpentine. This method requires little time, and often 

 gives excellent results, but it is not always to be relied on, though in 

 the early stages it answered very well, and the penetration of the 

 paraffin was facilitated. When chromic acid mixtures were used, the 

 specimens were brought gradually into absolute alcohol, which was then 

 replaced by clove-oil, and finally by a saturated cold solution of paraffin 

 in turpentine, before being placed in the melted paraffin. As a staining 

 agent hfematoxylin was used to some extent, but the best results were 

 had with safranin and gentian-violet, the latter especially giving par- 

 ticularly beautiful colouring, the nuclei being much better differentiated 

 than with the other colours. 



Staining of Vegetable Tissues.f — M. C. Sauvageau recommends the 

 following process. If a section is treated with concentrated sulphuric 

 acid, the cellulose-walls disappear almost instantly, while the inter- 

 cellular cuticular coatings (the protoplasmic layer of Eussow) remain 

 unaffected, united to one another by the median lamellae which separate 

 two contiguous cells ; but the rounded walls of the cells and of the 

 intercellular canals have become rectilinear. After the action of the 

 sulphuric acid, the delicate network which remains may be stained and 

 preserved in the following way. If some grains of fuchsin are added to 

 the sulphuric acid, the liquid becomes orange-yellow, or even dark 

 brown if the quantity of fuchsin is sufficiently large. A drop of this 

 liquid placed in much water gives it a rose-colour, like that given by a 

 drop of fuchsin to alcohol. The very thin sections are laid in a droj) of 

 dark brown sulphuric fuchsin, and covered by a cover-glass. Some 

 drops of water are placed by the side of the cover- glass, and a piece of 

 blotting-paper — which should be made from flax, and not from cellulose, 

 in consequence of the less action upon it of concentrated sulphuric acid 

 — placed on the other side in order to remove the sulphuric acid and 

 replace it by the water, and as this is gradually effected the orange- 

 yellow colour turns gradually to red as if coloured directly by the fuchsin. 

 The section is then composed entirely of the cuticular coatings of the 

 aeriferous canals united by the median lamellae. If the sections are 

 treated with sulphuric acid and eosin, the cell-walls swell, and the 

 cuticular coating is very clearly di&tinguished from the cellulose by its 

 greater refringency. The parietal cytoplasm is coloured rose, and the 

 punctations in the cell-walls are readily seen ; there are usually one or 



* Ann. of Bot., ii. (1888) p. 243. f See ante, p. 254. 



% Morot's Journ. de Bot., ii. (1888) p. 400. 



