NOTES. 
MICROSCOPICAL TECHNIQUE. —The series of processes and technical 
methods employed between the fixation of plant-materials for cytological investigation 
and the completion of the preparations are, in many instances, open to considerable 
improvement and call for full inquiry on physical lines. 
It is proposed to consider in short notes, of which the following is a first instal¬ 
ment, certain difficulties which have arisen in the course of cytological work and to 
suggest methods by which they can be overcome. 
The Stretching of Paraffin-ribbons on Glass Slides . 
Considerable difficulty is often encountered in securing perfect stretching of , 
paraffin-ribbons on the slides on which they are being mounted. This difficulty can, 
however, be easily overcome if the slide on which mounting is to be conducted 
be uniformly heated to a temperature closely approaching the melting-point of the 
paraffin concerned, and maintained at that temperature until perfect stretching is 
secured. A method found successful is as follows: 
An earthenware pot with a concave bottom (such as a ‘ shrimp pot ’) of about 
3 in. in diameter and i-| in. in depth is employed,. It is inverted in a metal dish 
(say, 7 or 8 in. diam.) containing water. There should be sufficient water to 
completely fill the pot and to allow the inverted base of the pot to emerge from the 
surrounding water by about ^ in. only. The water can be easily raised to a temperature 
just below the melting-point of the paraffin employed, and maintained at this tempera¬ 
ture by a small Bunsen flame or by a spirit-lamp. The slide on which the ribbon is 
to be mounted is flooded with albumin-water, or either Land’s gum-arabic-chromate 
or albumin-chromate fixative, on which the ribbon is floated. 1 The slide is then 
placed on the inverted concave base of the pot, which now represents a shallow dry 
basin, on the rim of which the slide is resting. The shallow basin is now flooded by 
means of a pipette with cold water until the whole of the under surface of the slide is 
in contact with the water. The slide gradually acquires a temperature approaching 
the melting-point of the floating paraffin-ribbon, which is gradually and uniformly 
stretched as heating continues. When no further stretching is observable, the slide 
is removed from the rim of the basin and most of the surplus fixative is drained away 
and the ribbon stranded on the slide. Any surplus fixative can then be removed with 
blotting-paper before the slide is laid aside to dry. 
In dealing with very thin ribbons, in which wrinkling is commonly pronounced, it 
1 Bot. Gaz., vol. lix, p. 398, 1915. 
Annals ol Botany, Vol. XXXVII No. CXLVII1. October, 1923.] 
